1997 Volvo 850 P0500 Repair Successful!

[donc]

This is a posting on how I solved a P0500 transmission problem on my 1997 Volvo 850 GLT Turbo wagon.

SYMPTOMS:
The car had been working perfectly and one day on the freeway with cruise control enabled, the upshift orange arrow of doom began flashing and the check engine light illuminated. The speedometer and other dash gauges still worked, but the engine revved high. From a standing stop, the car would accelerate normally and into 2nd gear and stay there. Winter mode allowed me to manually shift the car from 1st, 2nd, and 3rd, but was an unworkable long term solution as winter mode does not let the converter lock up.

FIX:
Evidently these transmissions have an input sensor that measures engine rpms and an output sensor that measures transaxle rpms. The computer does the rest. The code, P0500 revealed that it was a Vehicle Speed Sensor A Malfunction. This is the sensor toward the back of the transmission with one end of the sensor into the transmission kept by a torx screw and the other end into a modular socket kept by one of Volvo's wire retainers that you push in to release. I purchased an aftermarket sensor, Vehicle Speed Sensor VSS part number 9148788 and installed without correcting the problem.

I next purchased a genuine Volvo Engine Speed Sensor Incoming Signal part number 3515266 at $61.00 This is the one that connects to the top of the transmission with the torx screw retainer and the other end goes into the modular TCM plug socket. This socket comes apart with a little screwdriver on one side and a little pair of pliers on the other. There is a video on the web that details this procedure and if I can find it again, I will post it.

If you find yourself replacing one of these sensors, do yourself a favor and purchase the genuine Volvo part. The difference in the look and fit of the modular plug and the amount of insulation on the wires is amazing! Its worth the few extra dollars to get the genuine part!

Well, I still had the problem. This then when I unplugged the VSS and replugged it back in. There was a click of the wire retainer when I plugged it in, but I pushed further and heard a second click. For good measure, I pulled the Transmission Control Module TCM and the Engine Control Module ECM and replugged them in and then cleared the P0500 code with my reader.

Viola, the car ran flawlessly! I purchased the genuine Volvo part from VolvoPartsWebstore.com and wholeheartedly recommend them for clarity, illustrations of every part for EVERY model year, and price. There was a redesign of these transmissions in 1996 so look carefully before you order for the right model year. Here is a link to the parts for my car:

http://www.volvopartswebstore.com/showA ... odelYear=0

Look at part numbers 37 and 37b. For others like non turbo, diesel, and other stuff, there are pages for everybody. Good Luck!