Rick, on line 2657 of your datalog the main accelerator signal goes to 0.04 volts. anything below 0.50 will put the car in limp mode.
At the same time your sup accelerator signal stay good around 1.3 volts.
This tell me the supply voltage to the pedal is good.
on line 2692 of your datalog the main accelerator signal goes back to up to 0.86, a normal value.
An the accelerator pedal is operating correctly. Once the car goes into limp mode it will mot recover until cycling ignition.
And if not that wire, it may be time to look at the ECM. The fairly consistent 10 minute time to limp sounds a bit like it could be an ECM internal heat issue. I've read that they almost never fail, but you've checked pretty much everything else.
It would be fairly easy to strap an ice pack to the ECM to see if you can get past that 10 minute mark. If so, you may have a simple cooling issue, or, worst case, a faulty ECM with a heat sensitive connection, like a broken trace that pulls apart when heated.
I'm impressed by your perseverance, Rick. That's bound to pay off shortly.
He’s on his second pedal, I would focus on the wire.
I agree if he has already replaced the pedal.
The red wire is shielded by a ground wire. So it is possible that the wire got pinched somewhere during it's life. An easy test for this is to disconnect the ground. 650e9bdf.jpg
Rick, Did you splice the wires going to the accelerator pedal? If so, That is where i would inspect first.
This is a chart of the Accelerator voltage . You can see that voltage drops below 0.5 volts multiple times.
I'm impressed by your perseverance, Rick. That's bound to pay off shortly.
RPG
My perseverance is due largely to you guys helping with suggestions on what to do next. Otherwise, don't know what I would do.
Letting it idle on the driveway might work, but how would I know if/when it goes into limp mode? If I data log and check for low Accelerator voltage that would probably work. I'll keep this in mind, but other things I can check first. I have considered if it is engine compartment temp triggering it. The ECM (or ECU, seems to go by both names) is in probably the coolest spot in the engine compartment, but heat could still be an issue. I've never felt its temperature right after a drive, so I'll consider that.
I didn't notice the Accelerator voltage dropping so low just before it goes into limp mode. Good find there Bob. In the first log I was looking at when it went to 0 and figured that was the start of the limp. But it could have been the 1 line before that when the voltage drops to 0.02V that kicked it into limp mode.
And in this latest one, it is always above .68V until it drops to 0.04V at line 2657 and it goes into limp mode. Even though the voltage goes higher later, it can't recover until reset.
Obviously that is significant and a common factor. I'll check the voltage on the red wire. It doesn't go into limp mode after hitting a bump or anything like that, so a bad connection doesn't seem like it. The grounding of the shield around the red wire (Q in the part of the wiring in the post above) goes to a joint connector that connects to another shield, and also with pin C6 on the ECU. Maybe electrical interference from somewhere that is triggering it due to a bad ground in that system? I'll check that. I'll also take off the grounds I find and clean them; I may have missed some of that previously.
I don't think I spliced any of the wires with shields on them. I'll take apart more of the centre console to see the wires. It is of course difficult on a completed car to see all of the wire runs.
Thank you once again for the help/suggestions. Back to the garage.
Haven't made it to the garage yet. I could run a new wire, but according to the schematic it should be a wire with a shielded ground. It isn't a huge deal to take the console panels off. I designed it to come apart without any tools to get at the wiring and fuseboxes that are in there.
Haven't made it to the garage yet. I could run a new wire, but according to the schematic it should be a wire with a shielded ground. It isn't a huge deal to take the console panels off. I designed it to come apart without any tools to get at the wiring and fuseboxes that are in there.
At this point, don't worry about not using shielded wire. Regular wire will at least get you running reliably.
I would pull the red wire's pin out of the connector at each end. Could be a bad crimp of a pin.
The red wire in the OEM harness is not long enough to reach the gas pedal. So i suspect it was spliced.
Bob
I do not suspect heat as the issue as all other sensors going into the ECU are working normally.
I did a chart with the sub accel pedal showing good signal compared to the bad main. chart2.jpg
I also did a chart on your battery voltage. It doesn't look very good. bat.jpg
Last edited by Bob_n_Cincy; 09-23-2023 at 10:51 PM.
At least I'm pretty sure it is. Maybe I shouldn't have said that.....I might jinx it.
I put another wire from the pedal to the EMU to parallel the red power wire. I branched it into the existing wires very close to the end connectors. I left the "stock" one in place. Went for a long drive yesterday evening and.....no limp home. Went for another one today, pretty long, and no limp home. My wife kept saying that now I have to disconnect the new wire and see if the limp mode comes back. So I went for a drive today and after 12 minutes I snipped the new wire and kept driving; no limp home.
Here is what I'm concluding. When asked in this thread if I extended the accelerator pedal wires I kept saying no, which is true. But I bought the car with the donor stuff already done, with the stock wiring harness in it. I didn't think that the pedal wires might have been extended at that point. I took the harness out and did a serious wire diet, but left the pedal wires alone. Looking at them now under the wire sheath, they have been extended and several times. Looks like the red wire from the pedal goes into a white wire for about a foot, then into another wire, then who knows as it disappears into a major bundle of wires.
I disconnected the wires at the pedal and the ECU and measured the resistance of the red wire. It was about 12 ohms, but was jumping all over the place when I touched the harness. Now with a digital meter it does tend to jump around when the reading is changing, but this seemed like more than that. So I attached my extra wire and went for the drives.
When it didn't go into limp mode with the new wire cut, I'm reasoning that my disturbing the original red wire may have pulled a poor joint into a less poor joint and it didn't loose contact.
There is no good way at this point to run it where the rest of them go, to the rear of the console and then through the firewall into the engine compartment. It would mean fairly major work to open up that path again. I'm thinking of running it forward in the console into the forward compartment, over to the right side rocker panel, through that to the rear, and then to the ECU which is on that side. Shielded wire does not seem to be easy to come by and I don't know if that is required now. If I run it where planned it will be behind aluminum panels most of the way that should shield it from any electrical interference. Thoughts?
If there is a way to pull the contacts from the plastic connectors I'll do that and add the new wire in properly. But I don't see how to do that.
A couple other things. The check engine light did go on part way through my first drive with the new wire. After I swore once or twice I realized the car was still running fine, and continued to do so. I checked the code when I got home and it is a new one for me:
I looked it up and it seems to be something like the system expected the temperature to be higher after that running time. I'm not really concerned at all about that one.
And yes, my battery does seem to be a bit on the low voltage side. I haven't yet gotten around to cleaning all the connections, so I'll make sure and do that. And if I need a new battery, not a big deal at this point.
This has by far been the most difficult car issue I've ever had to solve. If it is (and right now I'm very sure it is) just a bad wire/splice issue, then it is a pretty simple one to correct. But finding it......what a PIA!!
Again, I thank all of you for keeping me going and not giving up.
Congratulations Rick! Well done. Glad the fix is a fairly simple one.
If the red wire was extended with a bad joint, the others were probably extended too. It might be a good time to replace all 4 of the pedal to ECM wires. Your Hall effect pedal is awesome in that it has no sliding connection to go bad, but the signal is fairly weak. I recommend shielding at least the red wire. Running the wire behind aluminum panels won’t help that much.
Connect the braided shield to the ECM pin C6 BY wire. The other splices can be near the pedal and ECM. Let’s hope that’s the end of your pedal worries.
Congrats man, I've been following this and I feel like even sharing your stress from afar, I bet it feels great to have it nailed.
For the connector, you can depin/repin them if you have the right crimp contacts and seals, I've had mixed success re-using original connector housings. Maybe this one's ok since it's inside the cabin, any connector from the engine bay I've tried to depin, I have about a 70% success rate getting it all back together without breaking something, the plastic gets a little brittle with age/heat.
You can typically get either a connector + pins and seals, or a pigtail that you'd crimp your own wires to. The "right" way to do it is probably to get the crimp kit and run a whole new group of wires back. Be careful with the shielded one that it gets the shield trimmed back and secured (heat shrink) before crimping, then the other end near the ECU tie the shield to ground making sure you keep it isolated from the internal conductor.
I cut the heat-shrink from the extensions the original builder did. They were all twisted together and the heat-shrink applied.........no solder!?!?!?! One on the red wire did not look very well twisted, so that was probably the one that was giving bad resistance measurements when I moved it. This is kind of surprising since all the other work was very well done.
I am replacing the 4 wires that go to the ECU and I've soldered the extension connections on the other 2 wires.
The path the bunch makes to get from the rear of the console into the engine compartment makes it pretty much impossible to pull new wire through. I'll run it forward and then through the rocker area.
Just waiting for the shielded wire to arrive, or as HJS said "now we play the waiting game".
I've noticed a lot of otherwise good mechanics are total hacks when it comes to wiring. It's a whole different skill set.
I did most of my harness lengthening/shortening with this sort of splice, with solder then heat shrink over it: linemans splice.png
Then after I was done someone told me that a crimp connection was better than soldering for vehicles, since vibration over time can start to crack the solder, so I guess we'll see. Hope my harness isn't a ticking time bomb.
While you're in there you may want to look at the other lengthened wires since the previous builder probably did something similar. From memory, there's the brake and clutch pedal sensor wires, as well as one of the headlight bundles (forgetting if I had to extend the R or L one) I didn't end up needing to, but I've heard some people extend the starter solenoid wire as well. I remember earlier you had a code for starter voltage or something similar so that one may be intermittent too.
I do basically the same thing when joining wires; twist, solder, heat shrink. I have also read that crimp connections are better. I've done some crimped ones but I only have a cheap crimping tool. Apparently the good ratcheting ones do very nice crimps.
I've done soldered ones for decades and never had an issue. Of course I never keep cars that long, so I don't really know if they cause an issue down the road (hey, a pun!).
I'll have a look for any other previously done lengthening of wires.
I replaced the 4 extension wires that go from the pedal to the ECU. Grounded the shield to ECU pin C6 and everything is working well now. Kind of hard to believe that such a small thing (one shoddy connection) can cause such headache.
Gone for several long drives. Went to a cruise night and then another daytime "cruise" yesterday. Sort of a "where's Waldo" but there really isn't any hiding with this color:
So much interest in the car and many positive comments on the color; especially in the sun when the green takes on a gold effect.
I am getting some stumble now and then and it was dying when idling a few times. Got a P0301 error code (cylinder 1 misfire). I'll look into that but I don't think it will be as hard to track down as the previous issue.
Thanks: 
Likes: 
Reply With Quote
Originally Posted by Bob_n_Cincy
