Good day, I have an 89 XJ pioneer with AW4 transmission - modified with 3" lift, SYE, and 60mm throttle body. I hope this does not disqualify me from the"stock" threads..??? But the issue at hand should not be affected by these mods IMO>

So, when I went to adjust my TPS after installing a new 60mm throttle body, the Vref only reads 1.4 volts at the three wire flat ECU side, not the prescribed 5 volts. I do not know what the Vref was prior to swapping the throttle body, unfortunately. I have done cruiser54 ground services and replaced a bad primary ground cable and cleaned other grounds. I also added grounds at the radiator mount and from the intake manifold to the firewall. When I check vRef jumping directly to the battery ground, it is still at 1.4 volts. The battery reads 12.5 volts (engine off). and I have re-checked the TPS to make sure it has the correct "hand-shake" with the throttle body lever. The throttle body flap is visibly closed while checking the Vref. The engine was generally running fine prior to swapping out the old - very dirty stock throttle body for the newer bored throttle body. I hate to just order parts with only suspicions on the part status, but I went ahead and ordered a new TPS - it will be a back-up IF the TPS is not the issue. Any thoughts on where to go with this while I await the new TPS? It seems odd that my TPS might have failed at the same time I replaced the throttle body. Thanks in advance for any suggestions.

 

Are you backprobing it with the TPS plugged in, or measuring the engine side connector with it disconnected? I'd have a good look at the wiring harness, in particular where it jumps between the engine and the firewall. There seems to be a rash of damaged wiring there lately. You might also start unplugging other sensors to see if the voltage comes back up.

 

I am back probing the TPS while it is plugged in. I'll try unplugging the other sensors as the next check. Thanks for the idea. I'll let you know if this shows any new issues. Doug