Code 42 - Vehicule Speed Sensor

Hi, I have a 1991 jdm gt4. Each time I get on the highway (and only when I'm over 100km) the check engine light goes on (code 42.)

I was about to get the sensor replaced, but my speedometer works just fine... in fact the whole car runs great. I erased the code from the ECU but it keeps getting back (each time I get on the highway.)

Does anyone knows the part number for that sensor and where it is located on the car. Also I need to find a place where I can order this part online.

Your help would be more than appreciated !!!

Any idea of what else it could be (anyone had this problem before ?)

If your car has ECT a/t try to find if this code is stored in a/t computer's memory.
the sensor on 90 celica is located near speedometer head , one end connected to the ground and other end is connected to the engine and ECT computers' terminals.
the sensor itself is the reed switch [looks like glass tube about 3mm dia ,20 mmlong

Thanks a lot for your help Doctor J, your reply was very relevant but I forgot to precise that I have a manual transmission.

Here is what I've found on code 42:

(M/T)
No pulse is input from the speed sensor (SP1) bult into the meter during input of a 4-pulse signal from the vehicle speed sensor (SP2) on the transmission


I also understand that there is 4 ABS speed sensors located next to each wheels. Witch sensor should I check ? SP1, SP2...or the 4 ABS speed sensors. (As you can see I'm far from an expert !)

Another precision that might help the diagnostic... that check engine light goes on at 102km/h .... not at 100... not at 90, only when I accelerate from 100 to 102 !

Thanks in advance for anyone who has an idea to share !

Follow your speado cable to the transmission, there you will find what your looking for as it will have a wire connection on it. Note it's going to be a pain as its very a tight area and hard to see part on our cars, Good luck. The part can be order from www.1sttoyotaparts.com (http://www.1sttoyotaparts.com), but I don't have the part number. Go to your local toyota dealer and have them look it up then get the part number and then buy it from website.

Had a bit of time this weekend. I took a look at the sensor (part No 83181-20040.) It seems ok... no broken wire on connector...and when I spin it with a drill I get a speed reading on the dash. I guess I'll need to order a new sensor to get rid of the check engine. Its sad to pay about 200$ for a sensor when there is absolutely nothing wrong wit the car except that orange light !

If someone has another idea before I order the sensor pls let me know.

Thanks for your help !