tps issues after steam clean

I have a 2001 cherokee, 4x4, 4.0, left hand drive, automatic.

I recently pressure washed the engine compartment. Engine light came on and had a p0121 code. "Tps voltage not agreeing with map sensor".

I tested the tps with a graphing voltmeter. Tps tested good with proper voltages and no drop-outs or spikes. When the engine was started, the tps signal voltage jumped up from .8 volts to 1.3 volts with the throttle closed. With transmission in gear, the voltage jumped up to 1.6 volts. Throttle was closed. Tps ground checked good, 5v reference voltage was good too. After much frustration, I found the o2 sensor heater, dark green wire, was bleeding voltage into the tps signal circuit, the orange/dark blue wire. I cut open the engine wiring harness across the firewall and found the tps signal wire went over near the transmission dipstick into another harness and through the firewall into the transmission control module located next to the accelerator pedal. I did not want to open the entire engine compartment harness, so I bypassed the apparent unneeded 5 ft of wire. I cut the tps signal wire that goes over to the passenger side of the engine compartment, the orange/dark blue wire near the brake booster, and ran it into the tcm harness at the firewall. The tps signal circuit has a splice just above the brake booster.

So far this has fixed the "Ghost Tps issue". Tps voltage is .8 volts at idle, with trans in gear or not. I've driven the Jeep 50 miles and no light has come on so far... hope this helps out guys



Back story...Even though the tps and map sensor tested good, they were replaced out of frustration. I even installed an ecm from a donor vehicle. I followed the troubleshooting tree EXACTLY. It tested the tps circuit and it checked out ok. The last step of the trouble tree was to replace the ecm.

Please note- the conditions prescribed to check the harness was with key on engine off. The problem I experienced was with key on engine running.

Hope this helps out guys!!!

Also all connectors in the engine compartment were disconnected and sprayed with electrical cleaner, blown out with compressed air and reassembled in search of this problem. None of them have any bent pins or apparent corrosion.

When pressure washing the engine, cover the throttle body with a baggie, it has too many moisture sensitive parts. The TPS is very sensitive to water damage.

We must be neighbors, I live on the south side of the abandoned Chatsworth reservoir.