okamikai

Hi, I must say this is a very complete forum, and I want to congratulate all the effort put into it as it has been a very valuable source of information, thank you, kindly.

Now for my subject, I recently purchased this truck and have no regrets about it, pretty solid machine, but since I bought it I noticed the CEL would turn on after just a few minutes of running, and I noticed an obvious loss of power.

I did the jumper thing on the engine fuse panel to get the flashing codes from the ECM, only one code came up, 52. I have read about this plenty and it all points to the Knock sensor and/or the 'Pigtail' harness. Besides that issue the truck has been running well enough to move around, but recently my radiator cracked on a welded spot (not a job well done I suppose), thankfully I didn't let it overheat, got a new radiator in, new coolant, cap, and hoses.

When I turn it on it dies almost instantly, as if was being turned off, at this moment I noticed that the CEL was dimmly flickering, at this point I suspect that there may be loose cable, a bad ground, or something else electric related, I've ruled out timing since the engine runs fine, but just suddenly dies, any light on the subject would be most appreciated, thank you.

RJR

This dying has just started since you replaced the radiator, correct? Sounds like the fuel pump is not continuing to run, due to possibly not reconnecting the plug to the VAFM after your service work. Try jumping B+ to FP on the diag connector. That will cause the fuel pump to run continously once the key is on. If the dying problem goes away you know it's in the fuel pump circuit. The jumper is not a long-term fix - it bypasses a safety feature that shuts down the fuel pump if the engine quits due to an accident, etc.

okamikai

Thanks for the info, I will add that to the list, I will also add a link to a pair of videos; one from the dashboard CEL, and one with a clicking noise coming from the engine compartment.

okamikai

Hmmm... I must say no, now that you mention it, it did the fail before the radiator change, right when I was putting it into the driveway...

Gamefreakgc

Do a visual and resistance check of the wiring if you can for the fuel pump. There's the COR relay behind the glove box that has a history of failing especially if there's been water damage, as well as the above mentioned pins on the VAFM.

That's after doing the fuel pump jumper.

okamikai

The problem still persist, but i found a way to keep it running, the only way was to disconnect the TPS and start it, let the engine warm up and then plug it back. I'm supecting one of the problems could be the igniter since it doesn't happen at the same time, and the fact that its probably the factory one. I will add the links to the videos that I recorded with the clicking sound, and the dim flickering CEL.

okamikai

Update on unknown gremlin, changed all the relays in the engine fuse box and the problem hasn't shown up again. Thanks to all those who took some time to check on this thread to help out.

okamikai

Reviving the old post as the problem has returned even worst, this time it will start, but it will stall terribly, I'm not getting a CEL now at pre-ignition, and no codes with diagnostic jumper on, any ideas?

okamikai

I made some findings on the problem, so far I've found that the EFI relay is heating up a lot, I replaced the relay with a new one, but the problem persisted, could it be a short of some sort? Any light on the subject would be really appreciated...

Kalihi,HI

Aloha, I've been working on a similar issue. It all started with a broken fan bracket, and I decided to replace my water pump and timing belt while I was that deep. She started fine but had a noticeable loss of power and hesitation with acceleration. I then replaced my oxygen sensor and TPS as they were both out of spec. I also replaced my PCV valve and my valve cover gaskets and fuel injectors. Now she starts fine but drops RPMs and dies within seconds if I don't gas. I replaced all fuel pipe/delivery rail gaskets and there are no fuel leaks. Any ideas?

okamikai

I did some research on this particular subject and was surprised (but not amazed) that this is a common issue with this truck, apparently it has to do with engine compartment fuse box having weak wiring regarding the EFI Fuse and Relay connection. The infromation suggested that the wiring should be changed for one with better gauge, #12 > #10, also relocating, and replacing the EFI relay with a modern one, also helped in some cases. If anyone from the forum have any ideas or a way of verifying if this is true it would really help to shed some light.

Gevo

I have a strong suspicion your engine and body grounds are no good. Easy to check, check resistance between the batt neg and various points through the engine compartment. Also, check that your Econnector at the ecu harness has less than 1 ohm between bat neg.

okamikai

I see by your sig that you have a similar truck, have you had this issue? mine's M/T, and today it started fine revved it, and ran it, everything fine until just a few mins later it started stalling and misfiring, again as stated before, the EFI Relay would be way too hot for normal operation, there is no way the engine heat could have heated it that much. I will trace those ground cable you mentioned and will post my findings

Gevo

I have had other issues that slowly were fixed once I started re-doing my grounds. I have an automatic tranny.. shouldn't make a difference for your issue though. You can use the wiring diagram in this link to help find grounding points.
http://snjschmidt.com/wiring/

okamikai

So I decided to do the E connector test on the ECU, but then I noticed a smell that I'm awfully familiar with; burnt electronic components. As I took the kick panel off I noticed the burnt smell was really strong, so I decided to remove the ECU and inspect it, in the pics can be seen the discoloration of the board on those two contacts, I turned it around to find this diode with obvious signs of heat damage. I believe this should be looked into as it may be a mayor issue, also, referring to the wire gauge thing I mentioned before, given my experience with car electronics and electric components, the wire that connects the wire the powers the EFI relay via the EFI fuse is rather small in comparison to the one feeding power from the main relay. I will also post pictures about this, I hope this information helps...

okamikai

I suspect you may have the same issue I have with mine, I can pickup a faint smell of fuel when I get close to the engine, I believe is the plenum gaskets that could be bad, also, are you getting code 52 from ECU, I believe it is triggered by engine knock do to poor air-to -fuel mixture, correct me if you have to, for I'm not an expert...

Kalihi,HI

Well, I'm not getting any codes now. I did have codes for my O2 sensor and TPS, both of which I changed, since then no other codes. I replaced my fuel injectors, but am worried they may not be sitting right as the grommets on the fuel injector which holds it into the/against the fuel delivery rail seem squished/smashed a little bit...any ideas about that? Also where are the grounds you are referring to? Ever replace the fuel pressure regulator? Any tips? Mahalo!

okamikai

Did some thorough investigation about the heat damage to the ECU board, following the contacts on the board it lead me to the Vc pin which receives both the signal from the TPS and the VAFM, I believe there may be something going on that circuit because the ECU is signaling code 41 (TPS) on a brand new TPS, but it is not Denso, so that may be it, I don't know why would it overheat the diode so badly unless its shorted... still doing research.

Gamefreakgc

ECU's rarely ever go bad on these rigs... so something bad happened.


Almost every issue with the engine is tied to a sensor or wiring problem. Narrowing down that list can be difficult though. I'm assuming you've already checked resistances on the TPS, VAFM, ECT, etc. If you haven't, it really only takes a few minutes with the service manual and a ohmmeter or multimeter.


However, if it's a wiring issue you'll want to use your multimeter instead to check the resistance of the wire (if you multimeter leads are long enough) from the end of the ECU connector to the TPS connector. If it's low, you are ok. Test against some known good wires as a control. If not... well you found you issue! I think you are on to something with that overheated ECU circuit.


Also, does your engine harness or other components have any jerry-rigged add on components or some sloppy wiring? If yes, you might want to consider re-doing those correctly with a sautering kit. Butt connectors and T connectors might work ok for a stereo, but NOT for sensors and engine components since it'll change the resistance value of your sensors.


PS I went with an aftermarket TPS and it failed in 3 days (Beck Arnley). Put on a DENSO and been fine for 3 years.

okamikai

It figures why my TPS was so cheap, now that I think about it this issue had not shown before I changed the TPS, maybe thats why the ECU keeps signaling code 41 (TPS), it may be causing a short in the circuit, thanks for that it helped me think, I will post my findings...