Resolved 1G DTC 0014 Throttle position circuit malfunction

[dwb]

Out of the blue my CEL decided rear it's ugly head. Pulled the code - 0014 Throttle position circuit malfunction. Attached is a log with the engine off pressing the throttle a few times until WOT. I don't see anything odd on this log. When driving, it behaves mostly normal with an occasional and abrupt "buck" when accelerating. I noticed the AFRs went rich the one time I was watching my WB. I haven't logged a drive yet, I'll probably do that this evening.

Is this as simple as replacing the TPS? It's only got 280k miles on it. I haven't looked at the wiring yet, but I went through and repaired the engine bay harness 2 years ago.

 

[steve]

IIRC, a TPS fault (14) is thrown on two conditions. The TPS output voltage is lower than .2v or the voltage is higher than 2v and the IPS is on.

Wear on the TPS can cause dropouts of the output voltage and throw the fault. I've been through a couple over the life of my car. I'm sure you can think of other things that would cause one or both of those tests to fail but I'd start with a new TPS.

I didn't see a actual fault in that log but the behaviour you describe is consistent with an intermittent fault and getting a log when it happens might trap it.

 

[dwb]

Thanks Steve. I logged it last night but the fault didn't come back. So here's a log from this AM. At around 560 seconds it started showing no signal and then gets flaky after that. I'll definitely be looking for a new TPS.

Anyone have any issues with the aftermarket TPS like the Standard Motor Products brand? Unbelievable the OEM units are $250+

 

[steve]

Did you disconnect the IPS during that log? It was off the whole time even before the point when your TPS dropped out?

When the TPS wasn't responding were there time you were providing throttle input. I ask because the log didn't show what I would expect for a bad spot on the TPS.

 

[dwb]

Did you disconnect the IPS during that log? It was off the whole time even before the point when your TPS dropped out?

When the TPS wasn't responding were there time you were providing throttle input. I ask because the log didn't show what I would expect for a bad spot on the TPS.

Oh snap! I did not notice the idle switch but I see it now. Thank you, I will take a look.
Attached is another log from last night where it looks like IPS stopped working. Very erratic readings. I did not have an issue with TPS though (at least no CEL or bucking). Looks like I may have two issues going on here.

I'll have to get the IPS fixed and do another log.

 

[dwb]

This explains the IPS:

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[dwb]

A new TPS solved my CEL/bucking issue and the IPS wiring has been fixed.

Kind of a funny story, but this situation almost left me stranded. Since my IPS was completely broken, I got home from work (I was logging my drive home and TPS was working fine) and decided I would set ECMLink to simulate the IPS via the TPS. I didn't think much about it, I leave my laptop in the house, and I was off to get gas and pickup my daughter. I fill up and pull out of the gas station. Suddenly the engine has no power, I can't accelerate, it's bucking, and RPM wouldn't go above 1.5k-2k. It idles like a champ though.
It was at this moment I realized I f'ed up.

The TPS is now dead and is sending a signal to the ECU that it thinks it's 0% throttle all the time. With simulate IPS enabled, no matter how much throttle I gave it, the ECU was only going to let it idle. So it was like a super bad case of idle surge while trying to drive down the road. Fortunately I was only a couple blocks from home so I popped it in gear and idled it home ever so slowly. Thank you manual transmission and F you TPS.

One thing about daily driving a DSM, it's a requirement to have a spare car. I was a few minutes late but my daughter found out exactly why I keep that old Corolla around.

 

[jed344]

Personally i on every single car with link check simulate idle switch in link. When TPS is set correctly it works just fine and most car's i see have long ago stopped using the idle switch anyway. Simulating it did not kill ur tps sensor. That was just a crazy coincidence. Yes though we have a box of TPS and good ISC motors from over the years .