Been dealing with ECU issues.
The original unit has been diagnosed as bad (by me). Verified 100%. That's another story.
Have a couple of other units in hand to test with the car, they are also in original (not rebuilt / recapped) condition.

One of them was a total failure. Opened her up - zero physical capacitor leakage but runs the car horribly. Rough as hell, not doing cold-start warm up routine properly ... actual MISFIRES (first time I've seen an ECU do that), idle speed wrong ... crapola.

Unit #2 runs the car very well. All of the expected behaviour. Interestingly, one capacitor is indeed leaking out (the one, and only one on the first board when the top cover comes off). Same cap has taken a dump on the original ECU to the car ironically.

BUT ... when the key is turned to the "RUN" position, i hear a rapid fire clicking sound from under the hood for a few seconds and then the TRAC light comes on. If I turn the ignition off and then back to "RUN" it may (or may not) repeat this. Sometimes the TRAC light goes on, other times not. Either way, the car runs well. I'm guessing it's some sort of communication breakdown between the ECU and the Traction Control unit?

I have seen at least one thread on here referring to a the same thing but it was never resolved or explained.

Anyone else run into this? Is it just a symptom of the installed ECU (kind of my conclusion), just curious if anyone else has seen this.

 

Hello,

A video of the sound would be helpful.

Is this issue present with any other ECU, or without the ECU connected at all?
Are you sure the ECU you have is compatible with your car and the Traction ECU?

When the Trac Off Light comes on, go under the Hood and locate the Diagnostics Connector, remove the Jumper between Pins WA and WB, then short Pins Tc and E1, which will give you a list of Codes stored in the system, may give a hint on where to go next. Traction Control has a separate ECU, so there isn't much that an Engine ECU would contribute to it, at least nothing that won't show up somewhere else, like in the way engine operates. Without hearing the sound or knowing the codes stored, not even knowing the Part Number of the ECU you have installed, it will be tricky to have any definitive answer.

Hope this helps and best of luck!

 

Good point

Nope, just this one. ECU part numbers are the same across the board for years/models. I don't think any special ECU needed to work with TRAC.

I have an OBD1 scanner - no codes.

I'm pretty sure all of these systems communicate with the central computer in some capacity

For sure ... all input is appreciated.

As it turns out ... FOUR capacitors were dead or dying. They were replaced. Computer re-installed. Key to "RUN" position ... no more clicking! TRAC light now on persistently, where before it was a "sometimes on, sometimes off situation"
Silver lining, aside from this the car seems to be running VERY well. Exceptionally smooth, rock solid idle, nice throttle response etc. Many issues appear to have been solved. But that dang TRAC light!

 

I wouldn't put too much trust into them, not in this case, sometimes a good old trusty paperclip is a lot more trustworthy.

Yes, what I meant is that there is very little that could be messing with the Trac ECU, while not manifesting itself anywhere else. ECU could only send a set of signals to the Trac ECU, if those signals are screwed, it would show up somewhere else as well.

Just the right time to get the paperclip out, even if it will blink constantly, that will be useful information.

Hope this helps and best of luck!

 

OK. We have codes.
46: Short in main throttle position sensor circuit
48: Open or short in sub throttle position sensor circuit.
Interesting particularly that it would be both of those.

I went ahead and attempted to clear codes. 46 is gone, 48 remains.
Also interesting (with respect to code 46), the manual states "indicator light does not light up even if error is detected".

None of these issues were present until i installed the current ECU (reason for this - the original took a dump and would not run the car properly anymore)
I tried another known good ECU (before this current one) on loan for diagnostic purposes ... no TRAC errors.
Original (to the car) ECU, even in it's compromised state ... no TRAC errors.
ANOTHER ecu I tried (before this current one) ran the car very poorly ... no TRAC errors.

Current ECU (before recap) ... ignition in "RUN" position, 5 seconds of continuous clicking, sometimes followed by TRAC light turned on, sometimes not. Runs car well.
Current ECU (after recap) ... ignition in "RUN" position, no more clicking, TRAC light ON, Runs car well.
All roads lead back to this ECU (to me anyway). Maybe that clicking sound was the sub (secondary) throttle valve spazzing out?
Wish I had someone turn the key while I was watching so I could have known exactly where that sound was coming from

 

That's actually quite a useful information.

Can you list the Part Numbers for the ECUs you tried, especially for the one that you are using currently?

For Code 46, I would assume that it should trigger a CEL, as it is more or less directly responsible for the Engine operation, the fact that the CEL is off either means that the ECU doesn't acknowledge the sensor at all, or that it does get the Signal from the TPS, but doesn't send it to the Trac ECU via a separate VTH Terminal, as Trac ECU doesn't have a direct access to either the TPS Sensors. Also, the fact that the code cleared at the moment may not mean that it won't come back, could be what happened to all the other ECUs you tried, it just didn't have enough time to trigger the code, though I am not sure how long each was connected.

To make sure that you are not chasing ghosts, it would be helpful to see if both sensors are functioning normally. Below is a Pinout for both the sensors and the ECU, if possible, try getting the Signal on the ECU connector directly to avoid the possibility of damaged wires. Next, check that the Engine ECU is sending the signal out to Pins 8 (VTH) and 19 (VSH) of the Trac ECU, you should see a 0 - 5V Signal on them that corresponds to the Position of each respective TPS Sensor.



If you are getting the TPS Signal to the ECU, but nothing coming out on VTH and VSH Pins, then you may need to dig into the ECU again and trace the Routes from the connector to see if any are damaged. If you are not getting any TPS signal to the ECU in the first place, then you will have to inspect the sensors you have installed. While at it, check that the Idle Switch (Pins IDL1 and IDL2) are working and that the sensors are adjusted correctly, as those are used to determine if there is a Short in the TPS sensor.

Hope this helps and best of luck!

 

Original ECU to the car: 89661 - 24231
Next one I tried: 89661 - 24230 (worked perfectly) ; this one was used as a diagnostic tool to confirm my original ECU was the problem
Next one I tried: 89661 - 24231 (ran car poorly but no TRAC issues)
Next one I tried and currently in place: 89661 - 24230


I highly doubt this. When I stream live data the TPS is there and responding. I don't see how the car would even be driveable without a TPS signal. It is completely driveable.

I hear what you are saying but the X-factor in all of this is the currently installed ECU. it is the only one to display this behaviour and it was apparent at the first key on cycle. The other units were in there plenty long enough to set codes etc.

I would be very surprised if the sensors were the problem. 30 years of operation and they suddenly both became a problem at the exact same moment I plugged in a new ECU? Not buying that but anything is possible I guess.

What exactly is this device? I assume it's something other that the IACV? Does it tell the ECU when the TPS is at zero?

Most certainly. I feel like I'm zeroing in on the problem.
I kind of want the traction control working, It's the GF's car and she drives it all year round (winter and all).

The only other time there was a TRAC related issue on this car was a good ten years ago after a brake flush. I just put that down to air in the system. I bled everything as best as I could according to the manual but it persisted. Went away on it's own after a while never to be seen again.
UNTIL NOW!

 

And I won't even argue, while not impossible, it's quite improbable, but for how easy those are to check, I see no reason not to.

I keep forgetting that you have an OBD1 Scan Tool, could be that my envy creates memory blocks..

Oh it will be fully driveable, don't ask me how I know..

It's not a separate device, it's just a simple switch located Inside of both TPS sensors, it lets the ECU know that the Throttle is closed All the way and the engine is at Idle. Refer to the Diagram from the previous post, Pin 2 (IDL) of the TPS Sensor is the aforementioned Switch, that's why TPS Sensors need to be adjusted correctly if someone were to temper with those in any way.

What a car for winter driving.

Either way, the problem appears to be located, now it's only a technical matter to find out what causes it. It does seem like you will need to dig further into the ECU issue, seems like either the traces got corroded or the Output Transistor got cooked, preventing the ECU from sending out the TPS Signal to the Trac ECU, though I would still verify that nothing Leaves the ECU before calling it toast. It should be possible to make the Traction Control work even if the ECU turns out being damaged beyond repair, the only question is how deep are you willing to go..

Hope this helps and best of luck!