[bcPete]

Hi all, I've been lurking around this forum for a few weeks now trying to sort out an issue on my neighbor's 02 Rio (1.5L A/T). It will randomly hesitate or sometimes completely stall while driving and will sometimes not start when parked for a while. I've not experienced the stalling first-hand but have had it not start on me twice. These issues might happen once a month or multiple times a week. As far as I can tell from asking the driver, there is nothing she is consistently doing when these issues arise; she might be driving at steady speed, accelerating, driving slow through a parking lot, rain, sun, hot, cold....no pattern as far as she has noticed.
The codes that keep coming up are:

P1780 Torque reduction signal malfunction
P0727 Engine Speed Signal Invalid
P0560 System Voltage malfunction

Codes have been cleared multiple times and have come back every time.
I have searched through this forum and others as best I could and the only thing I have found is to try replacing the CPS to cure the P0727, which I did, and which didn't fix it.
I searched the KIA Tech-Info site and did the suggested steps to diagnose the P1780 code, which was basically to check a certain wire between the ECM and TCM and check for corrosion on the two connectors. The wire terminals looked good, no corrosion and the wire had continuity even when flexed. The only thing that didn't check out was the measured voltage on that terminal of the ECM/TCM was supposed to be 5V but I measured it at 9V but I wondered if it meant at least 5V and it was just lost in translation.

The P0560 basically says to check ECM connector for corrosion or bad wires, all look good. The battery seems healthy and there was never any low voltage/dead battery condition for as long as I have been looking into this.

At this point I'm not sure what else to do except to start replacing the ECM and TCM to see if that is the issue. Problem is that these are not cheap and the owner is a poor student who needs her car fixed on the cheap. She has already taken it to the local dealer and a few other shops but they all told her it would cost more to diagnose than the car was worth....

Oh and I almost forgot, when it wouldn't start I put a timing light on it and it had no spark when cranking and not firing. Cranked it for a while and as soon as it started sparking again it started and ran fine so I think it's safe to assume that this is not a fuel or timing issue.

Hopefully someone had some insight into this and can suggest something else to try first.

Thanks in advance,
-Peter

 

[dsolorio]

I would check the ground wires, more specifically on or around the transmission. Sounds like you already checked your wire harnesses, be sure to check the whole wire all the way around. Many people tend to check only one side of the wire they can see and not spin the wire to see the other side that could be burnt up.

 

[bcPete]

Thanks for the suggestion. I previously only checked the ECM and TCM connectors and harness under the dash. I've started pulling the battery tray etc out and unmounted the fuse box under the hood to be able to take a good look at the wires running around the top of the transmission to see if I can see anything obvious. I was hoping someone here would say "Oh ya those cars always have an issue with x wire or connector chafing/corroding"
How about the ECM / TCM? Do they ever need replacing?
The troubleshooting steps for the P0560 say that when the ignition is turned on it triggers the "main relay" to turn on...I was thinking maybe that could be something worth investigating. Does anyone know where that is?
I pulled the ECM fuse out and the dash still lights up and the car still cranks without starting so I guess it could be wiring between the fuse box and the ECM but it doesn't look like an easy job to troubleshoot.

The local wrecker has an ECM and a TCM for $95 each so maybe it is just worth giving it a shot and replacing them both......