On my way to work today, I looked down at the speedometer to check my speed in a 25mph zone. I was shocked to see that it was registering 45mph. Instintively, I hit the brakes, the needle didn't move.

I searched on the web and found a S.B. and tried it, it didn't work. Is it the speed sensor on the tranny or maybe another problem. Just seeing if this has happend to anyone else.

Thanks
Doug

BTW, its a 2002 Lorado

 

Anyone? BTW, all the other gauges work fine. I think I'm going to try the sensor on the tranny if nobody as any other ideas.

 

if the sensor on the tranny doesnt prove to be the source try taking the gauge cluster off and cleaning the connections then reconnecting the wires.

-Kyle

 

I changed the speed sensor and still no change. I really dont think its a connection on the gauge cluster. When I performed the SB that I mentioned, it causes the needle to cycle (swing), so the gauge connection seems to be working. I'm stumped. Where does the signal from the speed sensor go? To the PCM or another module?

 

My 96 Cherokee Speedometer/Odometer stopped working. Tach., Oil, Gas, Battery Gauges still work. Took Speed Sensor Gear out of Trans. Stuck my fingers in to check drive gear and felt several loose pieces. Pulled them out and found they were pieces of a plastic gear that went around drive shaft, that turned the speed gear. Have seen a couple of other similiar posts that shared they replaced the eternal gear with a Dealer steel part, costing $50. I will be heading to local dealer tomorrow to explore a replacement part & how to make the replacement.

 

The speed sensor on the WJ is a hall-effect switch that reads the teeth on the transmission park lock gear wheel very similar to the way the ABS sensors read wheel speed. This information is fed into the Can-Bus system and read by the PCM, compared with the TCM's gear info, and ABS wheel speed data. NOTHING is simple anymore. All the systems use the same data bus and everything is integrated.

 

My manual says that vehicles with these transmissions don't have speed sensors, 2000 and 1999 42RE and all 45RFE/545RFE.
I think you have a 2 wheel drive with the speed sensor located on the side of the trans tail, if you have a 4x4 it is on the transfer case. Did you take out the adapter or just the speed sensor? And did you cut off the old wire connector and solder a new one on, and making sure that you kept the wire at the original length? This is what my 95 ZJ 5.2 speed sensor looks like, one pic with the connector plugged in and one with it unplugged:

 

I was going to add that when some mechanics want to test to see if the sensor is producing voltage they will remove the sensor and use a battery drill to spin the pin that I have pointed out in the photo below. While spinning the speedo generator they will look to see if the speedometer dial corresponds with the drills variation in speed.

There's a FSM test with the parameters to test it out correctly, but when they have nothing else that's a simple circuit test that some use.

 

I beg to differ! The speed sensor is a switch like the crank sensor and screws into the side of the transmission. The t/case doesn't have it in it anymore.

 

I think that you are referring to 1 of 2 sensors Sir, one is the low speed shift sensor, and ohe other is the high speed shift sensor.

 

There are 2 speed sensors in the WJ. The input speed sensor and the output speed sensor. They are both hall-effect switches and the part numbers are the same. One reads the engine speed on the input shaft and the other reads the output shaft speed in the O/D housing. Go to wjjeeps.com and check it out if you don't believe me. The 42re only uses an output sensor.

 

The 518 trans and the NP 249 J TC connections:

Green speed shift sensor. Yellow speed shift sensor. Red transfer case Vehicle Info Center signal. Blue speed sensor.

 

Whatever! All I can tell you is my 2000 WJ with the 4.0 and 242J t/case has only one speed sensor in the O/D case and no hole in the t/case for a sensor.

Sorry, I don't wish to argue so I'm out of this thread.