3FE - Codes 12 and 41 (1 Viewer)

[PabloCruise]

So I finally got my Check Engine Light wired into the Pig and now that I can check codes, I find it showing 12 and 41.

Code 12 is for the RPM Signal (Distributor)
-No NE or G signal to ECU w/in 2 seconds after engine has cranked

Code 41 is for the Throttle Position Sensor
-Open or short circuit in throttle position sensor signal

Wow, I thought my issue was lying with fuel pressure...

My underlying issue was that the idle would break down once the engine got nice and heat soaked. I did an ignition system tune-up and advanced the timing. PO had it set retarded, I got a lot more power out of it, but idle issue remained. I thought maybe the computer really wants dizzy set for 7* BTDC, otherwise it throws code 12. So I re-set timing dead-on the BB and took it for a drive, re-check codes - first check showed all good. I switched off the key and checked again; 12 and 41.

TPS tested bad when I had the throttle body off, so I replaced it with one from parts store. I installed using FSM procedure, and then tested using procedure in FSM. I could not get the resistance values that I should have.

I guess it never hurts to look at actual data!

I have access to a 11/88 FJ-62 for parts. As far as I know, I can purchase dizzy and TPS from this rig.

I imagine a 11/88 62 is technically a '89?

My 3FE is an early '88, based on block #.

Does anyone know if '89 dizzy and TPS will fit a '88 3FE?

TIA,

 

[PabloCruise]

PS - is it common for 3FE dizzy to go bad?

 

[Kynot62]

My 90 was built 11/89. I don't think they changed the 3FE between 88 and 92. (They were also in the first couple of year models of 80 series)

Since you have an FSM do the check on the distributor, my friends distributor went bad but mine never has and I can't say I have heard about them dying very often. Sorry I can't say what if any codes he had but his problem was with starting after it ran for a short time then wouldn't re-start. Wait awhile then it would start. Problem was with the distributor, found it with the troubleshooting in the FSM.

Tony

 

[RockDoc]

I suspect as long as the electrical connectors match, you should be golden for parts off of the other truck. Is the harness intact? Or could the dizzy issue be hacked wiring?

 

[rfj62]

The TPS changed in '89, you should be alright though.

Specter Off-Road-Land Cruiser Parts - Search On-037-140

and they are definitely not interchangeable.

 

[PabloCruise]

The TPS changed in '89, you should be alright though.

Specter Off-Road-Land Cruiser Parts - Search On-037-140

and they are definitely not interchangeable.

Looks like they changed in 3/89?

Thanks...

 

[PabloCruise]

The FSM lists resistance specs for terminals NE and G of 140 to 180 ohms

My NE reading was 300 ohms - so clearly out of spec, but not by much?

Has anyone rebuilt their dizzy to fix NE or G signals?

 

[Texx]

Timing won't cause the code, my 62 has been well advanced for years.

 

[Rescue Wagon]

TJ,

If you want I have a dizzy out of my 90 you could try and see if it helps. I'm not going to be running a Toyota dizzy with my 2FE.

Let me know,

James

 

[PabloCruise]

TJ,

If you want I have a dizzy out of my 90 you could try and see if it helps. I'm not going to be running a Toyota dizzy with my 2FE.

Let me know,

James

James - sounds good! PM sent

 

[PabloCruise]

Timing won't cause the code, my 62 has been well advanced for years.

So does that just mean that your crank angle is advanced a few degrees?

ANd so the two G signals per revolution just drive the 2 different batch firing of injectors a little earlier?

 

[PabloCruise]

I fixed it!!!

I have some significant updates about my 3FE Pig since the last time I made a posting.

I hooked up a Check Engine Light (CEL) and checked for diagnostic codes. I got codes 12 (RPM Signal) and 41 (TPS). I replaced the TPS with a Toyota piece and swapped in a used distributor. While I had the throttle body off, I replaced the PCV valve, grommet, hoses, valve cover gasket and the “donuts” that seal the valve cover at the mounting bolts/studs. After this work, I still got codes 12 & 41

I sought the help of a friend who is more skilled in automotive electronics than myself. We started out tackling the Code 41 (TPS) first. Using the troubleshooting protocols outlined in the FSM, we discovered an open in the line between the computer and the VTA terminal on the ECU. We replaced this wire and then discovered no voltage at the VC terminal at the TPS – this means the TPS was not getting any power to issue a signal. We determined the line providing power to the VC terminal at the TPS was disconnected under the dashboard – wow!

I re-checked for codes and found that both code 41 and 12 were gone. I am not sure why code 12 went away now that the TPS was happy, but that is what happened. Now that the TPS was live and I had my timing set with some advance in the dizzy, my Pig had some pep in her step.

Fast forward to re-setting idle speed (golden screw) and re-checking timing… When I had the 3FE nice and warm and tried to set idle to 650, I noticed my idle was “hunting” or wandering up and down again.  When I was driving home from work on a nice warm day, I noticed the idle was stumbling while I was sitting at a traffic light. And, I was getting a code 12 again. So, back to the drawing board…

I went back to the friend with the automotive electrical background. He also has a smoke machine which is really cool, because you can use it pressurize a system and see where smoke pops out. Using the smoke machine, we found the gasket around the EGR valve at the intake was leaking. We fixed that and “smoked” the intake again, and found a very slight puff of smoke at the ISC where the plastic meets the metal. I pulled the ISC apart, flipped the o-ring and dabbed a little silicon in there. We buttoned everything up and fired the 3FE up. After it warmed up, the idle was stumbling. Wow…

We broke out the fuel pressure gauge and hooked it up at the cold start injector. Fuel pressure in the rail: 71 PSI!!! We pulled the fuel pressure regulator and tested it with compressed air, it would open to pressure. We then found we were unable to blow any air into the fuel return line. We traced the blockage back to the soft line between the gas tank and the hard line under the floor. After clearing the soft line, we blew out the hard line, blowing from the tank to the engine compartment. When we lowered the Pig (nice to have access to a lift) the engine compartment was nasty with the debris that blew out of the return line. I had it disconnected where the soft line met the return line on the engine, just behind the thermostat.

We fired the Pig up again and checked fuel pressure on the rail – all was good!!! We checked pressure with the vacuum line hooked up to the FPR, as well as with it disconnected. We then set the idle and let it idle for a good 20 minutes and the 3FE purred like a pussy cat!

The bottom line is that I believe my problems were caused by a clogged return fuel line. I think the ECU was doing all it could to manage idle when there was almost double the specified fuel pressure in the rail. I am guessing the ECU had injector pulse width pulled all the way in. But along the way I discovered issues with the fuel tank, and that I needed to pre-filter my external pump. I found my o2 and TPS to be dead. I found timing incorrectly set. I found problems in the wire harness related to the engine swap. I found a leaking EGR gasket that probably made for a good vacuum leak. I am amazed this engine ran at all!!! I am also amazed I drove it from Colorado’s Front Range to Moab, UT (and almost made it back home!) So I am glad I found these issues before finding the obstructed fuel return line.

I had tanked up just before fixing the return fuel line and noted 11 MPG. I cannot wait to see what mileage is now that the system is running 38 PSI vs. 71 PSI!

My only other observation at this point is that I think the 3FE may be missing some of that extra pressure in the fuel rail when I accelerate. I have in excess of 7 degrees advance in the engine (the BB is no longer visible in the window) and it felt nice when accelerating. Now that the fuel pressure is restored to spec, the 3FE idles flawlessly, but I think I am missing a little power. My plan is to drive it for a while and note any issues that may arise. I cleared codes on Saturday, I will check codes again next weekend.

I hope this info is helpful to other 3FE converts. This is truly how I learned to stop worrying and love the 3FE!