I'm totally stumped with this. I recently bought a '97 Jimmy 2dr. 4x4. Runs great while in Park. DTCs as listed in the title; hard shifting into D as well as 1-2. It typically will not shift into 2 until approx. 2,500 rpm, and 2-3 is about the same. Acceleration under WOT results in the same performance, with 3-4 shift at approx. 40 mph. Will not downshift unless manually doneso. One problem I have not read about anywhere is under normal accel., the computer will idle the engine up to 1,500 in 3 at approx. 35 mph. and will not come back down until stopped for 5 seconds or so. After this occurs, if shifting into P or N, the engine will go up to 1,500 rpm for another 5 sec., then idle down.

What I've done and what I know:
IAC resistance was tested and sensor was replaced.
FTP sensor resistance tested, OK. 5v reference circuit tested, no power.
MAP sensor 5v tested, no power from PCM; signal and ground circuits OK. Scanner reads 3.0
TPS sensor 5v tested, no power from PCM; signal and ground circuits OK. Scanner reads 0.0
EGR cleaned; reference circuit tested, no power.
All vacuum lines OK.
Fuel press. is 60 KOEO, bleeds to 53 after 15 mins.
ECT accurate according to Actron 9185 Autoscanner, temp stabile at 189 -191 degrees.

PLEASE HELP!

 

If you have no 5V reference from the PCM, then there is either a dead short on the 5V reference wires or there is a problem with the PCM.

 

I changed the VCM, problem solved. THANKS swartlkk FOR YOUR REPLY. Picked up a used computer from the local salvage yard for $40, dealer reprogrammed for $43; other shops wanted around $100. I guess economies of scale really come into play there. Anyway, I still have an idle issue. At cold startup, she'll wind up to 2G for a couple seconds, then settle down to about 800 rpm. When shifting into gear, it'll surge to around 1,100, and if I don't move, after a few seconds she will again settle to 800. While in motion, at approximately 32 mph in 3rd, I can notice the engine surge to 1,500 rpm, but there's a bit of a power loss. At about 40 mph, she collects herself and the power is back (this is all at part-throttle acceleration) but the idle will not go down until stopped for 4-5 seconds.
DTCs:
P0440 - EVAP system malfunction. This came up this evening. I'll read more about it in the morning.
P0507 - Idle rpm higher than expected. I've read this could be caused by vacuum leaks. I've done the spray test and came up with nothing, but that was before the computer was replaced. I'll give 'er another spray.
P0463 - Fuel level circuit high input. I know the sensor is faulty here. I had the tank down some time ago to fix a hack job on the wires and fuel lines done by the previous owner. I took the opportunity to check the resistance of the sensor, and it gave high readings, above parameters.

One other thing I noticed when I got her back from the dealer: the speedometer started to give a reading with the engine rev'ed up, starting at 2,500 rpm, and the reading would never go above 6 mph. This could be attributed to the computer's learning process, but I think it's worth mentioning.

Thanks in advance for any suggestions you may have. This forum has helped tremendously in many, many ways.

 

P0440 - Evaporative Emission Control System
P0463 - Fuel Level Sensor Circuit High Voltage
P0506/P0507 - Idle Control System RPM Lower/Higher Than Expected

Those will get you started.

If your speedometer is sticking, it could either be a problem with the gauge cluster or with the VSS sensor. The VSS sensor is easy enough to remove and clean. It will be located in the tail housing where the rear driveshaft connects to the back of the transmission or transfer case (if 4wd).

 

A BIG THANKS for the schematics of the EVAP circuits! You have a wealth of information that is invaluable, and your willingnes to share is absolutely appreciated. This will definitely get me moving in the right direction!

I apologize for the ambiguity about the speedo... When parked and with the engine rev'ed to 2,500, the speedo will begin to give a reading and will not go above 6 mph, approx. 3,500 rpm; it's as though there is a signal shorting into the guage circuit. It works fine while driving, so since the tail shaft is not spinning, the VS sensor should not be relaying a signal, correct? Is this a sign of a failing sensor, such that it is allowing voltage to "bleed" to the signal circuit? I have not tested the circuits, yet, to diagnose an intermittent short or open, but the sensor does give a constant reading to the computer and guage, and I believe it is accurate.

 

If you are stationary, there should be no signal from the VSS, you are correct. I am not sure what could cause this phenomenon other than possibly induced voltage of some kind in the gauge cluster. If you have a scan tool, you could monitor the vss output to see if it is picking up something when you rev the engine.