The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

  • Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;) It will also allow you to view images in threads.

Please Support JNZ Tuning
Please Support Fuel Injector Clinic

Resolved 1G Throttle Position Sensor Signal Problem

jmkoons

Probationary Member
29
0
Feb 16, 2006
Santa Barbara, California
I've run into this problem with my car as well:

http://www.dsmtuners.com/forums/tun...5-s-afc-throttle-position-sensor-voltage.html

However, my problem differs slightly in that both Datalogger and SAFC incorrectly read the TPS as full open, in spite of a functioning TPS unit.

Important to note that my SAFC has been connected for a good number of years, has controlled and read back sensor values correctly until very recently.

I've checked the TPS without the wiring harness connected and resistances between pins 1-4 and 2-4 are correct, and throttle position affects signal values continuously as it should. Issue seems to be with wiring or ECU itself. When I disconnect the harness at the TPS, the signal reading at SAFC and Datalogger both drop to 0%.

The signal problem came up suddenly on its own as I was troubleshooting an unstable idle during attempted smog testing. With any luck, the unstable idle is related to this faulty TPS signal, which went from intermittent to complete failure, so if I solve this I should be clear in getting it through smog check. I'm hoping to find something that has come loose or shunted within the splicing at the ECU harness, which I will check next. I had the ECU out a few weeks ago to check it and replace capacitors. Unit went back in and car ran fine for a while.

As the original thread wasn't listed as resolved, I'm looking for any others who ran into this problem - nonvarying 100% throttle signal, which was not due to a bad TPS. I don't have permission to post outside of newbie forums yet, so I couldn't reply to that thread. Thanks in advance for comments.
 
Solution
OK, so far I've been answering my own post, and here's more.

Checked the #24 and #17 pin on the ECU connector, and they are showing hot when car is on. I found other posts concerning the sensor ground question, and see there are other sensors which would be affected as well. Unplugging the O2, MAF, TPS, and thermal output sensors, the readings on pin #24 kept climbing up from about +6V to about +11V.

Ground seems to be drifting at the ECU, not caused by a faulty sensor as far as I can tell.

After pulling the ECU out, I looked closely at the backplane, and noticed one trace flamed out near the center, connecting to one of the mounted ICs. Sure enough, one side of this trace is common with pin #17 and #24, so this has to be the...

jmkoons

Probationary Member
29
0
Feb 16, 2006
Santa Barbara, California
Just found that my ground wire on the TPS harness is at +5V, which is somewhat expected, as the signal to ground voltage doesn't vary at the ECU when TPS is connected and when operating it.

What I don't know is WHY the TPS ground signal is energized.

Checked ECU wiring and everything seems to be OK. ECU ground wire (identified per the SAFC wiring diagram) is at ground potential (vs. vehicle chassis). I bridged the throttle body to chassis ground with a large screwdriver, and that had no effect (TB already had a good ground per resistance check to vehicle chassis, and the sensor ground wire is independent). I forced chassis ground on the ECU ground wire, and again no effect (this ground wire was also reading no potential compared to chassis ground, so I knew it should be OK).

One last thing I tried was grounding the TPS sensor wire to chassis ground. This had the effect of showing invalid TPS readings, starting at ~20% no throttle to 0% full throttle (reverse operation, with the wrong starting point.) I expected this, since having a +5V sensor ground wire is going to screw things up.

Anyone ever encounter energized sensor ground issues such as this? And to suddently crop up out of nowhere? If I have to run my own ground wire somehow and cut the sensor wire out, I may resort to this since I don't think I'm going to find where the hell this 5V is getting in.

One thing I'm not sure of is if I tie a chassis ground to the sensor wire harness, and remove the original ground wire, will this work? The ECU just has to read the correct voltage resulting from the coil in the TPS, so I'm betting that it would have a chance to fix the problem as a workaround.

:banghead::banghead::banghead:

This is ridiculous, and I'm really pissed at this $#!*(#@#%#&@&#$*!^$^%[email protected]#^* car now.
 
Last edited by a moderator:

jmkoons

Probationary Member
29
0
Feb 16, 2006
Santa Barbara, California
OK, so far I've been answering my own post, and here's more.

Checked the #24 and #17 pin on the ECU connector, and they are showing hot when car is on. I found other posts concerning the sensor ground question, and see there are other sensors which would be affected as well. Unplugging the O2, MAF, TPS, and thermal output sensors, the readings on pin #24 kept climbing up from about +6V to about +11V.

Ground seems to be drifting at the ECU, not caused by a faulty sensor as far as I can tell.

After pulling the ECU out, I looked closely at the backplane, and noticed one trace flamed out near the center, connecting to one of the mounted ICs. Sure enough, one side of this trace is common with pin #17 and #24, so this has to be the source of the drifting sensor ground.

I'll try to get someone to solder up a patch across this trace to check if that was causing all the issues I've had, or at least get it to properly idle again.

Should be much cheaper than a new ECU if this works.
 
Last edited by a moderator:
Solution

rEclipserGST

Supporting Member
1,704
55
Nov 17, 2007
Columbus, Ohio
OK, so far I've been answering my own post, and here's more. Checked the #24 and #17 pin on the ECU connector, and they are showing hot when car is on. I found other posts concerning the sensor ground question, and see there are other sensors which would be affected as well. Unplugging the O2, MAF, TPS, and thermal output sensors, the readings on pin #24 kept climbing up from about +6V to about +11V. Ground seems to be drifting at the ECU, not caused by a faulty sensor as far as I can tell. After pulling the ECU out, I looked closely at the backplane, and noticed one trace flamed out near the center, connecting to one of the mounted ICs. Sure enough, one side of this trace is common with pin #17 and #24, so this has to be the source of the drifting sensor ground. I'll try to get someone to solder up a patch across this trace to check if that was causing all the issues I've had, or at least get it to properly idle again. Should be much cheaper than a new ECU if this works.

My SAFC is also reading 100% for the throttle. I can not get above 1.5k rpms (20 mph). When I put it in Neutral and try to rev it, it takes a LONG time to go above 2k, then it hits 4k and I let loose.... Just installed: MDP sensor, MAF sensor, 560 injectors, 14b, tial wastegate off the manifold.

Keep me posted because I am down to the last of the last... which is checking the ECU. Lordy lordy, hopefully it IS that. I've swapped in countless parts, and here they are:

Turbo x2
Air Filter and Oil Filter
EBC, SAFC, OBD-II
Crank Pulley
Water Pump
Fuel Injectors x2
Oil Cap and Gas Cap
MDP sensor and MAF sensor
TPS
O2 sensor x3
Coolant Temp Sensor x3
Spark Plugs and Wires x4
PCV
Alternator x2
Battery x7
Timing Belt
BOV
Fuel Pump x2

I am running out of ideas. I will try to post a video soon enough. One of the car NOT DOING ANYTHING and the other of me trying to rev it. I have not tested for boost leak yet, I just ordered a TESTER. I've run around too much looking for the parts to build on at Lowes, Sutherlands, Home Depot, Jeggs, they don't have what is needed. I've checked and reclamped all pipes and clamps. I've even doubled up on some. Hopefully It's leaking from the TB or the ECU is garbage. Those are the only things I have yet to replace.

Let's get the Guru's and Pro's in here :pray:. I'm tired of this pretty thing sitting there for 8 months straight.
 

collin trossbach

Probationary Member
8
0
Oct 12, 2016
Chestertown, Maryland
OK, so far I've been answering my own post, and here's more.

Checked the #24 and #17 pin on the ECU connector, and they are showing hot when car is on. I found other posts concerning the sensor ground question, and see there are other sensors which would be affected as well. Unplugging the O2, MAF, TPS, and thermal output sensors, the readings on pin #24 kept climbing up from about +6V to about +11V.

Ground seems to be drifting at the ECU, not caused by a faulty sensor as far as I can tell.

After pulling the ECU out, I looked closely at the backplane, and noticed one trace flamed out near the center, connecting to one of the mounted ICs. Sure enough, one side of this trace is common with pin #17 and #24, so this has to be the source of the drifting sensor ground.

I'll try to get someone to solder up a patch across this trace to check if that was causing all the issues I've had, or at least get it to properly idle again.

Should be much cheaper than a new ECU if this works.
Did this fix your problem
 

steve

DSM Wiseman
14,452
1,391
Feb 3, 2002
St. Charles, Illinois
The OP hasn't been seen here since 2013 but I'm pretty sure once he fixed his blown sensor ground it fixed his TPS problem.

Maybe @rEclipserGST can address what his turned out to be.

I'll suggest you review how a resistive voltage divider works and figure out where your getting 12v from. The specific solutions for a factory ECU most likely won't apply directly to your AEM ECU but the general principles do.

BTW you can find out when a user was last here by hovering your mouse over their userid. (assuming a real computer not some mobile device)
 

collin trossbach

Probationary Member
8
0
Oct 12, 2016
Chestertown, Maryland
The OP hasn't been seen here since 2013 but I'm pretty sure once he fixed his blown sensor ground it fixed his TPS problem.

Maybe @rEclipserGST can address what his turned out to be.

I'll suggest you review how a resistive voltage divider works and figure out where your getting 12v from. The specific solutions for a factory ECU most likely won't apply directly to your AEM ECU but the general principles do.

BTW you can find out when a user was last here by hovering your mouse over their userid. (assuming a real computer not some mobile device)

That is helpful thank you sir
Good stuff Thank you
 
Last edited by a moderator:
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned VR Speed Factory

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Top