GzrGldr

1998 XJ sport with approximately 260k miles on it. During a recent trip to Moab, on the highway coming home my check engine light came on. My scanner only shows a P0700, no other codes. It does do live tests and component testing, so I set it to test the solenoids (which I had just recently replaced). Everything passed except for the Torque Converter Clutch test. The scanner said with Engine On, but not running, to put it in Drive and turn the TCC to "on". It said that the vehicle should stall, and it didn't when I did that test. Also, it automatically went to unlocked on its own.

However, I haven't had any problems with shifting at all, and when the money light came on, the vehicle was actually running better than it had in a long time with no shifting problems.

So today, I went out and tested everything using the TCM wiring harness testing procedure. Everything was within spec except when I did the Specific Voltage Test for the TPS (Step 7), It only read .11v at idle, and .25 and WOT. That is way below spec. I did a test at the TPS also with it plugged in and backprobing. Ground was fine and 5 volt supply side was perfect, however, the TPS Signal was still only .11v at idle and .25 at WOT.


I replaced the TPS with another one that I had picked up at a salvage yard a while back. It doesn't appear to be OEM, but I though it would be good for testing at least, so I installed it and got the same exact readings.

At this point, I am not sure where to go next with the testing. I know it isn't the solenoids, as they tested perfectly and in spec, as did everything else except the TPS. However, grounds all appear to be fine and all indications point to a failed TPS, but two with the exact same readings tells me otherwise. Obviously something is wrong, but I don't want to buy a TPS as it doesn't seem to be the problem. I've seen a lot of stuff about high voltage on the Signal side, but not much in the way of a low voltage reading. Looking for guidance and suggestions on what to test next.

agreen

I'd find splice 112 and inspect it first. If it looks fine, cut it and try the voltage test at the TPS again. I'm wondering if you have a short to ground in the wiring?

GzrGldr

Inspected the splice at S112 as suggested. Splice looked good, but I cut the leads to both the TPS and the TCM and tested it with no change in results. Also cut the ground to the TPS and retested and it didn't make any difference. I also unhooked all of the other sensors connected to that ground circuit to do the test.
Also, went back and re-performed the TCM testing as I did not perform the last two steps for Output to PCM once I got the problem readings on the TPS. Both CAV 6 and 7 are at only .04 volts, so way out of spec also.
Only thing I can think of at this point is a bad PCM???

agreen

You'll have to test the TPS voltage at the sensor with that wire cut. If you already put the splice back together, you can unplug the ECU, TCM, and TPS and check that pin for continuity to ground. I'd also test it for continuity from each point (TPS, ECU, TCM). If you're getting 5v and ground at the TPS, it has to be an open wire or short to ground on the signal wire.

(Sorry it took a while to get back. I'm working through a maintenance shutdown at my plant)

GzrGldr

I appreciate the responses and suggestions, Thank you. I did test at the voltage sensor with the wire cut before I put everything back together and it didn't give me any changes. Some additional info now though... I have an Autel MaxiDas scantool that is a pretty quality scantool. After I put all my splices back together and plugged everything back in, I plugged in the scanner and set the live data to monitor the TPS signals while I drove. The voltages were all reading in proper range using the scantool while driving. At idle, the voltage was .84v which is within the specs, and with WOT, it read around 2.8v, which is below the 4.98 spec threshold. At idle, throttle percentage read as 0% but at WOT it only reached up to around 75%. I don't know if that is normal or should be 100% at WOT.
After the test drive, I decided to go ahead and clear the fault code. Cleared the code, and check engine light went out, but before I shut off the vehicle, the check engine light immediately came back on. This is new since I fiddled with everything, as it would only come back before after a couple of drive cycles. I cleared the code three times, and it immediately came back. Still only giving me a P0700 so not much else to go on. Everything shifts smoothly and normally, no hesitations in any gear. TC is locking up. I did the brake test and at around 55mph, I applied light brake while steady throttle and RPM's jumped about 300 rpm, so everything is working right.
I also replaced the TCM, since I had another one anyway to see if it was a communication issue there. Only other check is the PCM, but not sure how to test that unless I have another one to swap and see if it makes a difference.
One other thing that I did that may be causing the check engine light to come on automatically, is that I did reset the PCM using the scantool, as opposed to using the battery disconnect method. I know it requires around 50 warm-up cycles for the computer to re-learn, but would that have caused the check engine light to automatically come back with the most recent code?

exasemech

[QUOT
One other thing that I did that may be causing the check engine light to come on automatically, is that I did reset the PCM using the scantool, as opposed to using the battery disconnect method. I know it requires around 50 warm-up cycles for the computer to re-learn, but would that have caused the check engine light to automatically come back with the most recent code?[/QUOTE]

No

agreen

The voltage readings from the TPS are still highly suspect.

I'm also wondering if since the only code it's giving you is P0700, is the CCD bus open going to the TCM? The CCD bus is the "Chrysler Collision Detect" circuit, but in essence it's a multiplexing bus that multiple signals can go across. If it's not communicating with the ECU then it could give you that code too.

GzrGldr

It's definitely a communication issue. Going to try this test when I get a chance next. Found it on another thread. Although, it isn't an issue with no communication at all, worth trying. Going to go back through and clean up all the grounds again also. Maybe I missed something.
CCD Bus test

GzrGldr

RESOLVED. It was a bad ground wire at the G101 connection. I had removed it initially to clean the ground terminals at the very beginning of this problem and it seemed fine, but apparently I didn't really inspect it close enough. The crimped terminal connector must have been hanging on by a thread and I just didn't notice it. Explains the intermittent check engine light at the beginning. When I went back to try and check those terminals again, the ground wire was completely broken off of it, explaining why the CL just automatically came on even after being cleared and not driven. New connector, some solder, and all is back to normal.

Thanks for the help leading me in the right direction.