Dean Posted August 22, 2020 Report Share Posted August 22, 2020 Hi everyone. Link Fury, 1.5JZ. I wired it in over 2 years ago and it’s been faultless. I have an issue that only started recently. First with a trim pot switch (the AEM one), and has now appeared in my TPS sub signal. - ECU is showing a steady 5v output. - with the trim pot and now TPS sub, once the voltage gets to around 2.5v it just starts to drop gradually. - this causes an error in the TPS. All other sensors using 5v reference are fine. Oil press, fuel press, ethanol, pedal position etc. here’s a video of the trim switch. Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 22, 2020 Report Share Posted August 22, 2020 Connect a multimeter to the AN input pin at the same time so you have something to reference. Quote Link to comment Share on other sites More sharing options...
Dean Posted August 22, 2020 Author Report Share Posted August 22, 2020 Hi Adam. Do I just try to ram the multimeter into the back of the ECU plug? My main issue is with the TPS sub doing the same thing. Because it constantly reverts to limp mode. Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 22, 2020 Report Share Posted August 22, 2020 Push a pin or straightened out paper clip into the ecu plug beside the wire until it touches the terminal, then put your probe on that. https://youtu.be/Spy8AXlxVT0 Quote Link to comment Share on other sites More sharing options...
Dean Posted August 22, 2020 Author Report Share Posted August 22, 2020 it’s giving me the same result. that’s the trim pot switch rotating as in the earlier video. This is how the TPS is reacting. (Full throttle, letting off slowly) TP main/sub and AP main/sub all share the same 5v and GND, so i'm leaning towards a fault in the TP Sub AN wire. Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 22, 2020 Report Share Posted August 22, 2020 Now probe the 5V wire on the rotary pot and see what that is doing. Quote Link to comment Share on other sites More sharing options...
Dean Posted August 22, 2020 Author Report Share Posted August 22, 2020 5v is constant over the whole range of the switch. Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 22, 2020 Report Share Posted August 22, 2020 So if its got a constant 5V going into that switch, but the voltage fades away when it is biased more towards ground that would suggest the ground connection is weak/has high resistance/bad connection. You could try measuring resistance from the ground pin at the pot to the ECU sensor ground pin, it should be very close to 0ohms. Quote Link to comment Share on other sites More sharing options...
Dean Posted August 22, 2020 Author Report Share Posted August 22, 2020 If I’m doing it right. It starts at 1.5Mohm and slowly increases..... Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 22, 2020 Report Share Posted August 22, 2020 That would suggest you a break somewhere along that sensor ground wire, or a bad crimp at one end, or a bad splice. Since both the pot and TPS are affected that would suggest the bad connection is somewhere before it splits out to those two devices. Sometimes you can find it by wiggling different areas along the wire while watching the omhmeter. Quote Link to comment Share on other sites More sharing options...
Dean Posted August 22, 2020 Author Report Share Posted August 22, 2020 Thanks so much for your help. I look forward to chasing my grounds tomorrow! Quote Link to comment Share on other sites More sharing options...
Dean Posted August 31, 2020 Author Report Share Posted August 31, 2020 I chased every sensor ground, and removed almost the entire loom from the car and they all came up good (except for 3ohm resistance on one wire from the original Link loom sensor ground splice. Replaced that to be safe). - I finally tried another E throttle body and that fixed the issue up the front. (original TB was damaged in a crash about 5 events ago, so it must've finally given up) - I also tried another trim pot switch and that also fixed that issue too! (I'll do some tests on the switch and probably try to get a refund) So everything seems to be good, and I have confidence that at least the sensor grounds are good because they've now all been checked! Thanks again or your help. I've learnt some new things from this experience! Quote Link to comment Share on other sites More sharing options...
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