CharlieHustle

1992 4Runner
3.0L V6 engine

I've got a check engine code 12 that I cant seem to pinpoint the cause of. The light will go on and off intermittently, never completely ON while driving. The light will illuminate usually when downshifting under acceleration and then turn off as you approach coasting speeds.

So far I've replaced the spark plugs, cap, rotor, Spark plug wires.

I've checked the resistance of the G Pickups at the distributor and all three were within the acceptable range.

Is there anything else I can check? Maybe monitor something at the ecu? Or anyone with advice on how to tackle this issue?

CharlieHustle

BumP for any help?

scope103

You've done what I would have done. You're looking for an intermittent loss of the G or NE signal, which you might be able to detect at the ECM, but probably no more reliably than just watching the CEL.

Since you don't report a serious drivability issue, I'm going to guess that the magnet in the distributor rotor (not the replacable rotor, but the one down inside) is just getting weak, so that under certain conditions you don't get enough signal. Alas, the only way to tell is to replace the distributor; at $155 (RockAuto, Cardone reman) you probably don't want to do it on spec. You could also have a "slightly" bad wire back to the ECM.

Good luck!

CharlieHustle

Thanks for the reply. I was hoping for a fix besides replacing the dizzy but I guess not.

Real quick: Does the condition of the wire sheathing on the shielded wires going to the distributor matter? I have a few spots where its cracked or missing. The wire shielding is still present and not damaged, its just exposed. I've covered it with electrical tape at the moment.

scope103

So you might have water inside the cable. Which could (almost certainly) cause an intermittent problem. (Which will only get worse.)

I would try to replace that cable (as difficult as that is) before replacing the distributor. But I'm really just feeling in the dark here.

CharlieHustle

If there were any water, wouldn't the temp inside the engine bay dry up that water over time?

phil in Tx

have you checked the pickup coil. i was getting the 12 code and replaced mine. mine was on a 2.4 l though.

CharlieHustle

The pickup coils as in the NE, G1, and G2 points of the distributor? I checked them at the distributor connection point and the resistance measured within the values stated in the service manual. The air gap between the points and the rotor also were within spec.

CharlieHustle

Bump for any more ideas?

Team420

I would try replacing the igniter... Pretty sure I have seen those cause the cel #12. Grab one from a boneyard on the cheap, and if it fixes the problem, there ya go, if not, start searching for a dizzy

In fact, now that I give it more thought, b4 you replace the igniter, try cleaning the grounds, it grounds thru the bracket that holds it to the inner fender....

CharlieHustle

OK 3 years have past and I still have this intermittent code 12 CEL. I've tested the distributor with a multimeter.

G pickups were @ 153 ohms and NE @ 196 ohms.
There's no play on the shaft and air gaps measured 0.3mm.
Replaced distributor with junkyard part...nothing chnaged.
Replaced Ignitor with 2 different ones from the junkyard...nothing changed.
Distributor plug is fine.
Cleaned up grounds @ firewall and ignitor mount.

Am I missing a component or area to check here?

The runner starts up fine when cold or warm. At idle, the CEL will turn off. Once I hit the throttle, the light illuminates again.

I can't pass smog without solving this issue. Any help would be appreciated.

CharlieHustle

Just checked the Distributor pickup terminals @ the ECU plug while hot.

G Terminals = 192 ohms / 186 ohms
NE Terminal = 226 ohms.

I'm ruling out the distributor at this point. Ignitor seems to be fine since no change in condition after swapping with 2 other used oem ones. NGK Plugs and Wires are fairly new with around 5000 miles on them. Cap and rotor were replaced at the same time with the plugs/wires.

I guess re-checking the coil is next on the agenda.

CharlieHustle

Updating this thread in the event others encounter a similar issue of their own. I've finally managed to rid my 4runner of the CEL code 12. The culprit was the one piece I hesitated to replace because it tested out fine on a multimeter: the distributor.

2 years ago, I went to the junkyard to pick up a replacement distributor and swapped the original one out. After clearing the ECU, I start the engine only to still have an illuminated CEL. Checked the codes again and still a code 12. Tested the distributor according to the procedure in the service manual and everything checked out fine. At that point, I ruled it out from being the problem.

Time passes and registration on the vehicle needs updating, but not without passing a smog check. After changing out the ignitor, coil, cap, rotor, and ecu, the CEL still remained on. Removed the loom around the engine harness to inspect the wiring and found nothing. As a last ditch effort, I pick up another distributor at the junkyard and swapped it in. Problem finally solved.

Resistance and air gaps on all three distributors measured well within the allowed specs. The car never had an issue starting or producing spark. I assume the electronics within the distributor itself were to blame.

Motley

Has anybody had a code 33 before? Mine just threw a 42 & 33. I'm working on the 42 but have no idea about the 33

scope103

There is no documented code 33.
http://web.archive.org/web/201211190...85diagnosi.pdf

What Make/Model/Year are you working on?

Terrys87

iTrader: (1)

I am glad you updated this. I had to replace a distributor due to not being able to find the problem. I wasn't sure if I fixed it with the replacement distributor or the problem just had not presented itself again. Thanks for the update. I have spent hours trying to fix this in the past and just was not sure what it was.

Another part I have ran test on and even disassembled and cleaned contacts in is the TPS. It will pass checks with flying colors but install it on a truck and it fail. I am starting to think that no matter how good the test is, with the age and miles some parts are just worn out.

There is a truck I worked on and it wont throw a code in normal operation but when you jumper the diagnostic port, it will throw a code. I have replaced parts with new factory parts and tested everything and still get what I call a Soft Code, no Check Engine Light but will give a code in test mode. I am starting to think something along the lines of Scope that the wiring is just starting to get worn in these trucks and not sending a clear enough signal to the computer in some cases.

Motley

Scope, I'm working my 94 Toy PU EXT Cab with a 22RE & 5sp man trans. This is the second time that it has ever broke down. 1st time was last year when the pickup coil in the distributor came apart, it looked like a rats nest, but no light ever came on. Ignition Coil checked out good per ohm test by vendor manual. So replaced the pick up Assy, rotor, cap, and even an ignition coil. Betsy ran great up to the time it stopped at 242061mi. So looked at gap again on pick coil and reset to .011. Noticed no play in the distrib shaft and ignition coil checked out. So plugged in hand reader and it showed codes 33 & 42. Just thought I asked the question about 33. Still working on the no spark part in spare time

scope103

I'm not sure what you mean by "hand reader." As you can see from the FSM page cited, you just need the SST (we here all use a paper clip) to jumper TE1 to E1, then you read the flashes on the CEL.

The "OBD1" readers I've seen for a Toyota are electrically just a $30 paperclip. But yours might be fancier (readout?) In any event, I recommend you try the "FSM" method to check your reader.

Motley

Hahaha. My reader is a Scan Tool from Innova mod # 3140. I've tried the paper clip thing a few times over the years and have never had it work. I bought this reader to work on all sorts of trucks, GM mainly, and thought I'd try it on my 94 Toy. Low and behold it worked! I unplugged the MAF to see if it did work, and sure enough it did. So this is where the code 33 came from

CharlieHustle

The engine wiring on these 4Runners is exposed to so much heat and provided with very little protection as it routes around the engine assembly. I found a good number of connectors within the harness that were broken or appeared extremely brittle. I think the connections at the end would be the cause of a bad signal to the ecu. But never rule out the ECU being the problem....

Out of curiousity, I removed the covers from the ecu case to see if maybe I could find an obvious issue, such as a burnt board or capacitor. While everything appeared normal, I did catch this :


I'm still confused how that capacitor made its way there. I compared this board to 2 identical ecu's and found only one capacitor occupying C080 on their board.