Expert: Roland Finston - 8/4/2011

Question
QUESTION: 2001 voyager trans currently in limp mode. Deep scan indicated bad speed sensors. Both replaced. No improvement. Electrical involvement indicated as speedometer goes from peg to peg intermittently while stationary at a stop light. Fuel gauge is wacky also. Possible involvement of ignition switch (not cylinder).... key will not always work.

ANSWER: Hi John,
On the instrument cluster try a calibration. With the ignition off, press and hold the trip odometer reset until "sof #" appears, then release the button. See if anything further shows up in the odometer window. The guages will then calibrate.
I don't know what to make of the trans without further codes.
I am unclear as to what else is involved and what might be the cause.
Roland

---------- FOLLOW-UP ----------

QUESTION: This worked for a few days then the speedometer messed up again. Recal did not work this time. I thought that was strange. Any thoughts on this?
also, my 2001 pt cruiser is throwing a 118 code. Anyhting you can advise will be greatly appreciated!

Answer
Hi John,
You mentioned that it might be the ignition switch/speedo/fuel gauge/speedo. I wonder whether you might have some sort of a poor/flaky connection from the + post of the battery that is affecting multiple systems. One wire to look at would be the thinest wire of the three on the + post clamp which is possibly orange in color (actually a fusible link). I was told that it tends to get flaky from corrosion at the battery post. It is needed by the cluster and some other units.
The 0118 is saying that the voltage on the engine coolant temp sensor signal wire is too high suggesting a short of that to a wire carrying the battery voltage. You will find the sensor on the side of the thermostat housing, at the base of the coolant refill pipe. The sensor signal wire is tan/black and its ground wire is black/lgiht blue. Notice along the wire harness for any sign of melting of the insulation. Then check to see what the voltage is showing on the tan/black wire when it is removed from the sensor, compared to ground. It is attached at the other end to pin 26 at the pcm, while the ground wire is attached to pin 43 which a common ground point for many of the engine sensors.
Roland