I took my XJ to a shop to get my alignment checked. After they were done the shop owner tought he would be nice and power wash under the hood. When I went to get my XJ the check engine light was on. It was giving a TPS code. I changed the TPS and cleared the code. That code was gone but then code P0720 ( Output speed sensor ). I changed the sensor and cleared the code. The code came back on after about 2-3 minutes of driving. I changed the sensor again just incase the new one was bad but the code stayed on. At this point I don't think the problem is with the sensor, I think the problem is with something getting wet under the hood. I've done a lot of searching and the only other thing it could be is the ECU or possibly the old speed input sensor messing with the new speed output sensor. Please help.

Today while I was driving the speedometer was all over the place. It would not keep up with my true speed.

 

[QUOTE=nicksdsm;1215256]the shop owner tought he would be nice and power wash under the hood. QUOTE]
Sounds like the shop owner should be fixing your Jeep!

 

Hopefully you have receipts for TPS and speed sensors to bring back to garage so they can reimburse you. I'd also bring your xj to a good shop (or dealer) to fix it and submit that bill to the garage as well.. But I've had a long day so maybe I'm just extra cranky... :/

 

I let him have it for a day but he didnt seem to know how to fix it. And at this point I was really "mad", so I just took it. He's already refunded me for the alignment and has given me money for the new TPS and Speed output sensor. He's not going to touch my XJ again.

 

VTJeep : I've been dealing with this for a week now. I'm really cranky too.

 

The VSS signal wire goes directly to the PCM without going thru any other connectors. The PCM then sends a signal to the inst. cluster for the speedo. the VSS ground and 5V ref circuits are shared by many sensors and if they had problems you'd have multiple codes. I.E. the TPS code you had. Considering the pressure wash I'd recommend disconecting the PCM connectors and let them air out for a day. Make sure theres no water or corrossion in the conectors. Couldn't hurt to open all the electrical connectors under the hood and check for water!! Compressed air and or Delectric Cleaner spray may help too.
Good Luck!!

 

Thank you very much! I'm not to sure what all of that means but I'll talk your advice and unconnect everything and let it dry out. I did use an air compressor to dry out the PCM connectors. I did see a little water come out of the connector.