Crazy tranni on 2003 Pontiac Sunfire

Tranni won’t shift out of 1st. Speedo reads “0”. Have replaced speedo sensor and wiring plug going to sensor. Works until car has traveled a slight distance. Any ideas what else may need to be looked at? Husband is Mechanical, we just need ideas.

Have a transmission shop scan the computer. There are things that need to be monitored that only a scanner can do.


If husband is mechancal enough, he could check for a signal from the speed sensot to the computer. If the plug is disconnected at the computer he could connect a voltmeter, set to read AC volts, to he 2 wires from the speed sensor. Jack up one front wheel, block the other wheels and with the transmission in neutral make sure there is AC voltage tothe computer. If there is no AC volts, and the sensor is new there is either a probelm in the wiring, or in the transmission. You say it works until it has traveled a short distance, does the speedometer also work for a short time? Testing it while it is working will only show that it works now. One other test, take out the speed sensor and try to move the toothed wheel inside the transmission, I have heard of this wheel coming loose on some cars, if it slips you do not get the speed reading.