I’m testing all systems after a complete rebuild. No sure whats going on with my pedal or controller.
It’s a 2002 with a T2 controller, not sure if it worked before and haven’t had it tested. After powering up and clearing a few errors I’m now getting the -8 error code. I assumed it was the pedal so tested the OHMS. It tested fine. I unplugged the pedal and tested the 8pin connector that goes from controller to pedal. Pin 6 (Pin 8 at controller) is sending 4.8 to pedal as it should. Pin 8 (Pin 9 at controller) has continuity to ground. But the wiper wire at Pin 7 (Pin 7 at controller) is reading 4.6 volts. This wire is labeled as “ACCELERATOR INPUT VOLTAGE SIGNAL”. So it should NOT have any voltage when disconnected from pedal, right?
Tomorrow, I’ll see if theres a short somewhere in that wiper wire but I’m guessing it might be a short in the controller? Anyone ever seen this?
Thanks in advance!!
That seems a bit high… Any chance something is wedged under the back of the rocker / top half of the pedal that is forcing it down? On the driver’s side of the pivot? IIRC, if the pedal is depressed in any way at key-on, it will throw an error code. The stock floor mat is just thin enough to slip under the back and just thick enough to raise the back which pushes down the front of the pedal enough to send a signal.
The accelerator pedal in the 99-04 GEMs is a bone stock Linemaster TIG welding pedal. It’s been a while I’ve had one open, but IIRC, there is nothing inside it but a variable potentiometer and a spring. You can pop the pivot shaft out pressing on one end (side) of the shaft with a punch or a phillips screwdriver that you don’t like much…
If the pot is fried, you can order one from Linemaster direct for like $30. You may have to call them to order or get the right part. Or you match it up though Digi-key, Mouser, Grainger etc…It’s nothing special.
See chart. You may have just posted wrong. If not, pot wires got reversed. Does pin7 go low with throttle? Controller pin 8 is low side of pot, pin 9 is high side.
Pin 7 must be less than 0.9 volt. And less than 1.4v when start switch is closed.
Open throttle where it’s easy to meaure pot volts. If correct, maybe cogs slipped. Adjust as per above.
Pot burned out or no B- to low side= no change to pin7 and fault -8.
Thanks! I’ll be doing more testing today. I have anew potentiometer on the way. Does anyone have a picture of it installed? Want to verify that it’s wired correctly. if look at the top (where the stamp is) the left pin is the 5v, middle is the wiper and left pin is the ground? Thanks!
East to test all the wiring from inside. ~4-5v from top to bottom of pot. 0.5v to wiper. Wiper voltage going higher with pedal? Going lower the outer two wires reversed inside pedal or harness. Not likely!
If you have the 5v supply but wiper stays high, then wiper trace is burned open. When open the low side of pot cannot hold the wiper below the required .9v at key on.
To set up new pot timing:
Set to .5v at zero throttle.
Simulate pedal movement and make sure switch trips well before 1.4v.
WOT should exceed 3.5v, 4v+ is better. I don’t recall the high limit before faulting, but 4v should be safe.
Thanks! I tested even further and it just got weirder. I pulled the 23pin at controller. Ran B+ to pin 1 then tested pins 7,8&9 on the actual controller. Getting 3.6v on the wiper pin. So looks like i have a short inside the controller thats feeding volts to the wiper pin. Time for a rebuilt i guess
No, you can’t test with cable unplugged. Turn on car and test wires by piercing insulation.
You need to follow my instructions if you want me to help.
I suggested testing inside pedal. You have full and easy access inside without risking controller damage.
Just curious… what errors were you getting? And what was the root cause & resolution?
As @Inwo stated, opening the pedal up and testing at the junctions at the potentiometer is the best and safest way to test. You can just just clip the meter leads on the terminals and watch the readings as you twist the pot knob. Another very good reason for opening the pedal and testing there is that piercing the insulation will often rot your wire away from the inside unless you live in an exceptionally dry climate.
@AssyRequired thanks for the pics! Mine is wired the same.
@Inwo i appreciate the wisdom and i did follow your guidance on testing the pot first. I got 5v at high, ground was good. Wiper gave me 3.6v at all positions. Thats what wasnt making sense. So i removed the pedal from the 8pin connection. Same readings. Wiper still had 3.6v. So im thinking short in the hardness between IP and the controller. I pulled the 23 pin from controller. I have a 23pin “tester” plug. Its a 23pin connector with 23 lead wires not hooked up to anything. So i ran 72v from lug to Pin 1. Batt- was still connected. 72v at Pin 1 is all you need to energize Pins 7-9. Again 5v was good. Ground wire good. And wiper is still reading 3.6v!
@JarJarJava
Error was -8. High voltage at wiper. No resolution yet. Why would i be getting 3.6v at Pin 7? Probably a short insode controller? Any chance whats a controller setting that someone screwed up? Like i said. Its the first time ive powered up this equipment. Who know what the PO has done to this thing
[he says with such confidence]
Clarify what you mean when you say this.
How EXACTLY are you testing the ground?
(Describe what you are doing exactly and clearly) Mainly, what are you using for meter reference? (where are your meter probes touching when you are checking ground?))
Anyone know if theres a controller setting that would supply voltage to the pin 7 wiper? Wouldnt think so but haven’t explored the controler parameters that deeply.
Don’t jump ahead. You tested to have good voltage at Pot high and low, no change at wiper means bad (open) pot. You did test from pot low to pot high to get you reported readings? Not from some phantom common.
Mid voltage at p7 is normal measured with high impedance meter. Controllers are designed to use two wires of pot, in many cases. Parallel meter with resistance equivalent to the pot for accurate reading. 5k-10k. Or not. Stop looking to spend money and put in the new pot.
Tip: Whenever I am testing [something] and I get some strange/unexpected result, I try and figure out another way to test that [something] and see if it gives the same result or something different.
Try this:
Safety: Whenever you are working with throttle pedal, it is a good idea to have the front wheels off the ground in case you touch the wrong wires and the car decides to take off across the garage and attempt to park itself inside the dryer.
Conditions: Main Batt Sw ON.
Meter set to DCV 200v scale(whatever you have)
Black meter probe on the ground wire at the pot (the red one)
Red meter probe on B- (Neg post on the controller)
What do you get? (expect 0)
Then move the Red meter probe over to B+ (Pos on the controller).
What do you get? (expect PackV)
Yep. I tested the pot high to low. No change in resistant. Tested high to wiper. High resistance with no “gaps” then low resistance when pedal down. Tested low to wiper it was exact opposite of the high to wiper test. I was still reading 3.6v at wiper regardless of pedal position. I pulled the pot and replaced it with a pot from a spare pedal. Same results. A constant 3.6v a wiper at all times.
@AssyRequired
Yep. Front tires are off ground. I have a clip on the black probe. When testing 72v i clip to the Batt neg lug on controller then use red probe to test the 72v circuits.
For 12v testing i clip it to the chassis neg bolt. Probe 12v with red probe
