hello yotatech,

was out looking for a slight project and finding myself deeper than expected. have had a few vehicles, but mostly doing brake and suspension maintenance, did not prepare me for troubleshooting electrical issues.
my truck is a no-start at this time but has gotten to that point as i've tampered with it. please see story below:

purchased this 1989 pickup, 4x4 3vze automatic, with 280+ on the odometer and receipts for a head gasket rebuild, water pump, and injector service which occurred two years prior/25k mi ago. i took ownership july 2020.
truck was owned by single family but went from father to son to grandfather. signs of aftermarket stereo install and under-budget engine rebuild abound, but grandfather stated "truck is well-maintained."

I drove the truck around after popping the hood and crawling under it. No rust, and no apparent signs of miswiring to the uninitiated. The truck started and ran fine on the first crank both times I got to it for test drive. I now assume the owner was warming it up prior to my arrival for the classic "she starts every time!" I did notice the truck didn't go into 4th (o/d blinking) but does cycle through all 4wd gears. decreased my offer because the truck seemed fine and still won. should have known...

the pickup ran fine on the way home, a 15mi drive, and did a few grocery runs during the summer. Replaced the engine coolant temp switch and have it going into OD no problem, no blinking light. I drove it to the auto parts store to pick up fluids and spark plugs, and it wouldn't start when i came back out. I sat for a moment and to get myself calm, and cranked it again, it kind of stumbled and then ran fine. made a beeline home with a sense of alertness but it died one more time when turning in to my neighborhood. again I was blessed and the truck cranked up while moving (no power steering for that moment) and i got it home, a little shaky that I had endangered others with this mystery condition.

kept it parked and told myself it was something intermittent/not serious. decided to drive it in to work to share it with another yota enthusiast, a 3vze owner who is now having random deaths while driving, and it sold me out- died in an intersection 20mi from home. seattle cops drove by me on the way to starbucks and a buddy pulled me to a safe side street. parked it and came back after work with intent to diagnose, but the POS started right up and gave me some false hope. I went and picked my wife up from her job and got on I-5 south (away from seattle) only to have the truck die about 10 minutes on. bartered for a AAA tow to my driveway and since then, been collecting codes and reading yotatech. wife doesn't trust the truck and wants to see it fixed.

the truck has started a few times since then. when the truck was running, if i would move the ECM even by bumping it, the truck would die. I believe this to indicate bad grounds or something terrible in the circuitry.


current status:
truck is a no-start after I replaced the COR for fun and pulled out some disgusting black tape covering wiring. just wanted to knock out the easy one (COR) and expose the ECM over there for testing. ignition coil tests fine with ohm meter. distributor wires out test fine, have not opened dizzy. fuel filter replaced. fuel pump running when key is on. loud click from COR and good spark from ignition wire out to dizzy when grounded against frame. these very few engagements with the wiring seem to have caused it to crap out completely, because it would run tenuously before, and not at all now. Crank, a little combustion, stumble, die. No continuous run. haven't gotten into injectors at this time (actually never removed injectors before).

codes:
a/t code #61 defect in #2 VSS or circuit- can't find the damn #2vss on my A340H 4x4 and absolutely positive the circuit is messed up badly, merged grounds etc
3vze engine code #14- igf signal from igniter is not input to ecm for 6 consecutive ignition, open or short in IGF or IGT circuit from igniter to ecm, check igniter, check ecm (goes away if i pull the main efi fuse but comes back when the truck fails to start)
3vze engine code #51- Displayed when A/C is ON, IDL contact OFF or shift position in “R”, “D”, ”2”, or ”L” positions with the DLC1 terminals E1 and TE1 connected

current goal: fix above codes, have a running truck, swear by toyota manufacturing afterward

i think this truck has terribly modified wiring as shown in below pics. i also worry the 93 fsm I have access to may not be accurate to my 1989 truck. along with the desire to fix the codes, I believe i should repair the grounds in this system, which appear to be too few and too weak. especially being that the truck doesn't run after the heavily corroded unshielded 12ga wire from driver's fender to block was ripped out.

any early year 89-95 experts, i really appreciate any sharing of wiring diagrams or wisdom. in the meantime I will decompress... removing all the shielding and tape to expose this mess of wiring kind of took the wind out of my sails. I tried to remove this 14mm hex bolt on drivers side of engine block to which that corroded wire was mounted, and stripped it out. fun!

thank you for all the educative posts and hoping to document my truck's tribulations here for posterity. i'm ready to crawl under the truck every day but I have been a little shaken by the rat's nest in there this week.

 

 

Welcome to YotaTech.
Grounds? Could be, but there are a lot of wires going to and coming from the ECM. Breaking the connection to any one of them will probably cause the truck to die. It's really that simple.

I don't want you to over-correct, but your code 14 suggests a break (intermittent?) in the IGF wire. That won't cause the truck to stall, but losing, say, G or NE will. (And it will stall so quickly you probably won't get a stored code.)

While a problematic ECM can't be easily ruled out, my money is on a bad connection to one of the three ECM connectors. I'd start with a careful visual inspection to see if I could find any suspect leads.

 

Hot goes to starter and to fuse block. Neg down to starter? and little wimpy ground to fender. Ground is continuous but probably overworked.


Likely part of my code 14 with this corroded ground? Thing fell off when I stuck my hands in there. Truck didn't start after I broke this out.

Engine to firewall ground, looks like they crimped it after the engine rebuild

Thumbnail points at stripped bolt where I feel a ground used to/should be

 

Thanks scope for the reply. You and mudhippy are the gods I was praying to. I am with you in that the connections are likely bad. Here's a shot from the pass fender where you can see a bunch of brown (earth/ground?) wires merging, likely the root of the code #61

 

[QUOTE=scope103;52451750]
I don't want you to over-correct, but your code 14 suggests a break (intermittent?) in the IGF wire. That won't cause the truck to stall, but losing, say, G or NE will. (And it will stall so quickly you probably won't get a stored code.)

Scope, I have attached photos, it appears the IGF wire is continuous from ecm to termination at the igniter. I just wanted to eliminate a single variable.

Advisable to start tracing each brown wire from ecm to ground?

Black / yellow stripe IGF from ECM per next screenshot

3rd from left wire on rightmost connector facing outward from ecm

Need a length of wire instead of daisy chaining leads

Daisy chain

Continuous to before the plastic enclosure going under the manifold

Continuous to just outside igniter

 

Don't forget to wiggle your wires. If your multimeter has a "continuity function" (with beep) that helps.

You have the correct setup. Just be prepared to take your time and be as thorough as you can be. Catching an intermittent fault is just about the hardest maintenance item you'll ever do.

Any of your problems could be caused by bad grounds, but also by an intermittent open/short just about anywhere else.

Here's a drawing of the two speed sensors for a later-model 4runner. You are almost certain to have a cable speedometer in place of VSS1

 

Just some general observations, if I may:

The ground terminal on the battery is badly corroded. IF it were me, I'd replace it. I use "marine terminals", terminals that have a screw post sticking straight up. This means you need ring terminals on the wire(s) that go to them. Not only are these a lot easier to replace bad wires on, AND make better connections that are easily cleaned, but if you have more than one vehicle, all you need to do if you do something silly, like leaving the lights on for a few hours (ahem, not that *I* ever do that...), you can just remove the wingnut on the screw post, pop the cable(s), swap out for the other vehicle's battery, slap the cables back on, and away you go.
The ground cables from the battery both should be good size, I use 1-0. One goes down to the engine block, either on the AC compressor mount, or one of the holes it would use, if there is no AC compressor. Front passenger side near the bottom. The other ground cable goes to the fender wall, just forward of the battery. I'm not sure where that bare, broken, ground wire you found goes, but it LOOKS like it might be the ground wire for the alternator. If it is, it should actually go to the power steering pump mount. It should also be an insulated wire. The ground from the head to the firewall looks fine.

Your positive battery terminal: The heavy gauge wire down to the starter looks good, but that small wire going to the fuse box really should be a fusible link kind of wire, to protect the fuse box and all the circuitry from there on out. It also looks like, where it goes into the battery terminal, it might be breaking, and may well be corroded inside the connection. It also, to me, looks too small to carry all the current it needs to.

Several of the wires on the plug for the ECM you showed, including the one you tested specifically, look like they have been pinched at one time or another. Try wriggling them when testing. Wiring in vehicles move around a lot, and you need to test them while simulating such motions. It's entirely possible for a wire to break inside the insulation, but only actually not make connection when the wire moves around.

Remember, there's a very important ground inside the left (driver's side) kick panel. It has a pretty well known problem with the wires going into the terminal that screws onto that particular ground point to break inside the crimp of the terminal. As bad as the rest of the wiring looks, I'd check the fuse box, and connections, in that left kick panel, over carefully.

That one place where you have "many into one" brown wires, well, just unwrap the tape from around it and give them all gentle tugs. That will show any troubles. Alternatively, trace all the brown wires to their far ends, and measure from there to ground, if it IS a ground, while wiggling that connection point. If it is, in fact, a ground, there's nothing wrong with the "many into one" concept, as long as it's executed properly. If it's a crimp connection, there's the problem of making the wires all fit into it. If it's too small, many of the wires many be broken, where the connector crimps down tight. May LOOK good, buuuut...
It really should be a solder join, to avoid that situation. Not easily done, but it's more doable than a crimp connection. It should also have heatshrink on it. The "meltwall", or FIT-300 type heatshrink to protect it from the nastiness under the hood of a vehicle. Electric tape just don't cut it at all. ANYwhere in a wiring harness. Just my opinion, but I was a radar tech my entire working life, including in the Corps. I learned a few little things bout electronics, and electrics, during that time

Sorry I can't be of more help...
Pat☺

 

His battery is not the correct battery, terminals are reversed with the positive next to the fender. Looks like a factory link maybe in the sheath.

I've actually started replacing my battery terminals with marine grade quick disconnects after killing a few batteries. These marine terminals are epoxy coated and reduce the crusties quite a bit.

I will disagree with the crimped ground. Yes it shines on the outside but what does it look like inside. I'd just replace it! This is the shortest path to ground for the 3vze sensors there at the back of the engine. With the busted ground shown also this one at the back of the engine is the shortest path for the sparkplugs too.

ECU wiring. In addition to the wiggle test it failed already. I see an image of a meter probe inserted to a female connection. Unpin these from the plug housing and tighten them up so they bite the male lug. While you have them out give them a tug and see if the sheathing stretch's, they typically will start to show a color change before they separate where the wire is broken inside the sheathing.

I think you're chasing your tail a bit. You've already identified a problem near the ECU plugs and not resolved it. This is going to be a broken wire, a loose slot to pin, or a damaged ECU plug (bad/broken solder joint inside the ECU). Fix this first. If you still have issues I would move to the area of that taped joint, it shows signs of water intrusion any exposed copper here maybe corroded for instance the joint under that tape.

 

Thanks again everyone at yotatech, including scope and co_pu for helping me cobble together a fix. The wire was not being held securely into the connector by the lockable back strap (that's what I am calling that feature of the (molex?) connector) and as shown in the video below, it could get out about 1/32-1/16 inch, or 1mm of play. Any wiggling or jostling of the wires or ecm would instantly kill the truck. That's how I got stranded last time, and that's why my wife gives this thing the side eyes.

I used a bent bobby pin to remove the IGF wire by pressing the bobby pin into the same face where the ecm pins would insert. The bobby pin was maybe 15 deg bend over 1/8 inch. It is directional, use the photos above to guide you until you are familiar with the release method.

I crushed the very end of the terminal with pliers, knowing that if I exerted too much pressure, I would be set back by having to order terminals and crimpers. With that caution I made like three crushes while flipping the pliers 90 degrees to keep the terminal square. I tested the fit on the ecm pin and liked the bite.

I knew that the wire was still gonna be loose and I fathomed gluing, adding a spacer, and other shadetree methods of fixing the wire in place. When I saw that there was a female cylindrical shape on the inside of the locking back strap of the connector, I knew my wire had prolly just shrunken to where that shape was no longer biting into it. So to build the wire up to where it would be held, I selected ptfe tape, which maybe was not as good as black galv tape. However the shielding was in place and I knew that ptfe/plumbers tape would do fine. Three to five wraps and, with the connectors all in, I can jiggle and wiggle as if I was hitting train tracks or logging roads at 30mph. Engine is still running.

Thank you to all of the people who contributed above! I hope the info here helps others who have ecm / pcm wires that are loose. I also hope that those people consider buying new connectors and terminals when it benefits the quality of repair!!

Video link below:

 

Also 2toyguy and y'all have made some good comments about the quality of electrical connections. I will get a new battery and start cleaning up in the engine bay. That way we can all rest easy and maybe see some increasingly pleasant photos.

Cheers all!

 

updates - starting with the small and getting back to the main points above

replaced battery with a yellow top. buddy found a red top in the garage with a good warranty and i got a steal. connections replaced with quick disconnect marine style fittings. Ground is on the correct side. Funny yall said about the backward battery. A friend of mine had his battery short to the fender and caught the power steering pump on fire. Good thing I didn't drive around much with that improper setup. got a new battery hold down from rockauto. miserable that I still have to bush a $300 battery in with an ugly piece of rubber...

4ga ground to fender near fuse block instead of 14ga. need to do the one behind engine still.

replaced all light housings around the truck, blinkers in the bumper and in the grill, headlights (wish i would have read the sticky and gotten the hella LED conversions) and taillights. front right grill blinker is not functioning at this time.

remove and repair by sanding, the door courtesy switches in both passenger and driver door, neither worked. now the door locks will pop up automatically and the noise will sound if the keys are in the ignition.

remove both sides door panels to investigate passenger power window operation. could not roll windows down from driver's side control or passenger's side control. driver window operating fine, if a little slow. the passenger power window switch was indeed bad, replaced for $3 at rockauto. new switch did not give results, and multimeter read 300mV at passenger window switch. I isolated the two blue wires at the switch connector (they had an ohm of resistance across them, so i figured they were the wires to the window motor) and jumped battery voltage to them. the motor operated just fine. I started ripping the dash apart to trace the source of the other 3 wires at the switch connector, taking them all the way past the COR at passenger kick panel/glovebox, over to the ignition lock cylinder, then to the door control relay (blue box, mine is thankfully working fine), then to the driver's side power window/lock master switch. following the test procedure for that switch revealed that there was excessive resistance/no circuit for the full 12 v to reach all the way to the passenger window. the switch is fairly priced at $300 and after watching some videos on rebuilding Supra switches of similar design, I was able to GENTLY take the switch apart, sand some contacts, and replace. All door and window power features are working nominally and I only had to mess the panels up a little bit. I might fabricate something custom for door panels.

Idle was way too high at 1200 rpm in gear. I checked the throttle cable for play, it was okay. I dropped the idle by adjusting the slot screw head on the throttle body. it was going very low at 650 rpm in gear. seems like 4-600rpm drop from park/neutral to being in gear. that, and the truck didn't even move when idling in gear. wait for it, i'll tie this in below.

harsh engagement into drive positions coupled with the RPM drop had me start to wonder about the transmission line pressure cable (often called "kickdown" cable) which works with/against the throttle cable. there was a lot of slack in this cable so I did tighten it up. the bucking when going into drive seemed more intense or the same as before, so I backed the cable off to leave a very small amount of slack. The harsh engagement has completely subsided, but left me with a noticeable "chink" noise when engaging into drive or reverse. it's so stressful to me that I took a video for us. maybe this is because the harsh engagement caused an issue, like something got repeatedly hammered, leaving play? can someone help me identify the nature or cause of this sound, and maybe stop it? shifts are great and the truck feels immensely better when driving on the road but I worry I am damaging the transmission when I go to reverse/drive. I probably won't drive it unless it's an emergency, to prevent damage.


Hell could be u joint noise right?

adjusting the idle after the above cable adjustment has the truck idling at 13-1500 when cold, but 8-900 in gear, maybe 1100 when warmed and in park, then 800 solid in gear. i believe this to be better. the truck doesn't sound "rushed" as you might have guessed it did before.

Weeks ago I pulled out of a gas station near my home and while the shift control lever appeared to be in the D position, I did not experience upshift... Almost threw me for a loop. The appearance was misleading as I was certainly in 2 for SECOND GEAR and drove half a mile down a 25mph road at 3500 rpms. Sorry to abuse the truck. This was quickly fixed by getting under the passenger side, having someone wiggle the shift control lever from inside the vehicle, and isolating the linkage visually. there were 2x 10mm nuts which trap one arm on a slot. remove nuts, pull trans control arm all the way toward rear of truck (park) then push it toward the engine 2x (reverse, then neutral). Turn the keys on so you can move the shifter lever inside the vehicle and remove parking brake. I had wheels blocked with 4x4 timbers. Move the shifter to N and using a friend or a weight, press the shifter lever toward R (it's staying in N, you just want to gently press it toward R to take up slack) and then tighten the 10mm nuts on the linkage. My lever still has a lot of play and doesn't indicate which gear it's in very well, so there might be a bushing or something else that's giving play. However, I'm certain that I won't accidentally end up in the wrong gear again. Also, the truck would not run after this- the park/neutral safety switch is affected by this change, so I had to gently press the shift control lever toward P to allow the circuit to complete to the starter. if you get no starter noise, consider that...

i drove the truck to a jobsite and the guys at the site were pissed at me for letting the tires get low. it doesn't go without saying actually. check your tire psi hahah. and top off brake fluid. does this truck have any balancing option for brakes? i feel that it pulls to the passenger side when braking.

to the good poster scope103, i was struggling with wanting to make another post without addressing the first solutions you offered. testing vehicle speed sensor #2 at ECM seemed okay although it read 6V when keys on. I traced the wires using long leads and confirmed continuity from SP2 on the ecm connector to one of the wires at VSS#2 connector, severed harness does not seem the culprit. if you get the perfect angle you can get both hands on top of the A/T and disconnect VSS #2, if you don't you will fight it for a minute. I had to cut a zip tie to free the connector. Block the front wheels, jack the rear up and place both sides on axle stands, rear tires will be able to spin in park. manual says ohms should change to infinity when the wheel is spinning but I didn't get this result. combined with the voltage being off at the ECM, I believe VSS#2 is at fault. i posted a video because I feel the tests are conclusive and some may benefit from the visualization. will i pay $100 from rockauto and see any improvement in vehicle operation?


It actually took me almost a year to find and test VSS #2, so anyone reading should know to just do the hard work up front! those problems do not go away with time, they go away with hard work which takes time!

i have new plugs to put in the truck but want to get some ngk wires. anyone against that? buy oem? worried about buying them and having them melt and cause a misfire :O however lightly tugging one had the wire come out and the crimped connector stuck on the damn plug. can't be having very good spark with that situation.

finally i had taken the grill out. i was working in a composite shop and I felt compelled to sink 30 hours into making a mold of the grill. does anyone want a very expensive carbon fiber grill? the mold came out immaculately, and allows for milled/laser cut inserted features, and could have custom paint options etc. just seeing if there is any interest as I consider making a short run of parts.



okay all, please see the videos, I hope they help, and I would love to answer any questions... thank you for helping this truck get so much healthier than it was...

 

additional photos for context

 

 

commuted a few 20-60 miles in the truck because the engagement into gear sound isn't that intense. the damn thing is running like a top now, butter smooth shifts and not really powerful per say... but it's under 3k rpm at 70-75mph. check engine light came on. I worried a bit while driving 20 mi home. but then, at home, with special service tool, the diagnostic codes are constant blink OD light (nominal/no trouble code?) and still code 52 (i think because someone crudely tore the ac system out of here). and the CE light is not usually on because I disconnect the battery ground after typical operation.

check your brake pedal switch if your brake lights stick on. mine did this morning but not this afternoon. odd.

harsh engagement into gear leaving work but maybe because truck was cold? still checking that out. does not occur when warm.

I think this truck is doing okay. will get spark plugs and wires, and dump some seafoam through finally. i hope someone benefits from something here!

cheers,

kraptastic

 

It's been my experience the CEL( without a code) is either an 02 sensor, or the AFM needs adjusting

 

if you put new plugs in an old truck it just might blow the head gasket out. luckily I found out in the driveway and not at the city dump when I was in line. truck has been parked for a few months. got a 1990 Lexus ls400 and started removing it throughout the winter. had the boys over this weekend and we pulled the thing. I'll start posting again as I rip the 3vze out of the 89 truck. Open to any bids for a 1990 ls400 body (wrecked and without a motor/trans) and a for-parts 3vze motor.

For anyone still reading- the chink sound I was looking for was a driveshaft yoke that hadn't been greased in many many years. Get your driveshaft serviced (unless your motor is blown, then find something else to do)

Car: 1990 LS400 175,000 miles, two owners before me. PO wiped it out backward through a guardrail. Tan interior. Radio control is dead, and front sway bar was cut, but everything else is original.

Located in Tacoma, WA for anyone interested.












Next steps are to offload this red car and to get a body lift ordered for the truck, and to document the removal of the 3vze.

Cheers all. If you have swap parts or information please solicit me.

 

Top shift rf1a from 88 runner
Got transfer case
Got t100 automatic tail housing

Need $1000 in adapters, conversions and gaskets