The Nissan Path

I own a 1987(10/86) Pathfinder and I have a problem involving code 42 TPS. The input voltage is supposed to be variable from 0.5 to 4.0 volts and its supposed to change when the accelerator is depressed, but when I measure it I only measure 0.03 volts body grounded and 0.006v ecu grounded and nothing inbetween. I've tried using a different ecu and the same thing is occurring. I installed a new TPS and I've also checked continuity on all the wiring to the tps and everything is fine. I was measuring the voltage after installing and it all of a sudden dropped off and never returned. TPS was checked and is fine. Any ideas?

There are a number of steps in the DTC 42 diagnostic procedure. If you want, I can e-mail you the diagnostic charts. Just send me an e-mail at [email protected] and put in the subject line: "RE: 87 Path DTC42."

I've done that procedure from the start using an 89 fsm. same steps, anyway, still have the same problem. new TPS, ecu, all wiring continuity. so what am I missing? when I measure ohms from white to black while plugged I get 6 M ohm.

With the ECM and TPS disconnected, check for continuity to ground between a chassis ground and the white wire as well as the chassis ground and the P/B wire; there should be none and if there is, you have a short to ground in that circuit.

Next, w/ ECM and TPS still unplugged, measure the resistance with an ohmmeter of the white wire at the TPS harness connector to the white wire at terminal #19 of the 20-pin ECM harness connector. There should be continuity and minimal resistance (about 0.002-0.003 ohm). Next, do the same check with the P/B wire at the TPS harness connector to the P/B wire at terminal #25 of the 16-pin ECM harness connector. If either of those wires are "open" (no continuity), you have a broken wire. If either of those have a reading above 0.003 ohm, there's excessive resistance in the circuit. Let me know how you make out!

Another tip, just because parts are "new," don't automatically assume they are "good." Go through with the tests as described. I've been bitten by that bug more than once!

I unplugged the harness from the tps and the ecu. I then checked between terminal e (white signal wire) and ground and there was continuity, about 0.6 ohm.

So I was looking at the wiring diagram and it looks like the white signal wire to pin 19 is always grounded through joint connector A. The air flow meter had the same thing on the diagram so I checked its harness the same way and it was grounded as well only I have no problems with that sensor. So, naturally, I'm as lost as ever.

87Fathpinder wrote:I unplugged the harness from the tps and the ecu. I then checked between terminal e (white signal wire) and ground and there was continuity, about 0.6 ohm.

If you have continuity to ground on the white wire with the TPS and ECM unplugged, that means the white wire is shorted to ground and that's a problem. You should have gotten a reading of no continuity, or "open circuit," to ground. The white wire is the signal wire and is also shielded in the harness. It may have rubbed through the insulation and shorted to the grounded shield covering the wire, or it may have shorted somewhere else. Regardless, you need to trace the white wire and find out where it's touching ground.

Problem solved! Thanks... the signal wire was grounding to its shielded casing like you said. The internal insulation was dry rotted about 3 inches down the line. So now I just repair the wire and call it good. Now I just need to take care of my code 43.

Glad you got it fixed!