Resolved 1G No O2 signal and no Tach

[wishihadatalon]

Alright, I finally have this car running but after getting a logger hooked up, I realized I didn't have a TPS signal or O2 signal. I finally figured out the TPS signal (broken wire) but after doing so I no longer have a tach signal.

I did the 91-94 ECU in a 90 on here where you run a new wire down to the ECU and everything was fine, but after messing around the harness, my tach no longer works. The wire was exposed, is it possible that I messed something up grounding the wire on accident? I did a continuity test back to the PTU and the wire is fine all the way to the ECU.

Also, I did a continuity check on the signal wire for the O2 sensor and that checks out as well. Initially I was trying to run the O2 with the simulated output on my wideband but wasn't having any luck. I have tried 2 different stock sensors, but I don't think its a sensor issue.

Any input that you could provide to help me get this car running will be very much appreciated.

Thanks

Update if anyone is following: RPMs work again. Not sure what I did here, just pulled the connections apart to check continuity and put it back together. Gonna have to check these over again and make sure the pins are in good shape.

For the O2: When I got the car, it was a wiring nightmare (still kinda is) and the previous owner had some gauges. I had a black wire coming from out of the passenger side kick panel. It was black so I assumed ground but it wasn't going anywhere (must have cut it when I took everything out before) so I grounded the pin. Once I figured this out, I get O2 voltage but nothing that cycles. Not sure what temp the car needs to get up to before it goes into closed loop, but I reached 157 degrees before I shut the car down. Gonna try tomorrow to see if I can get it cycling.

 

[Soccerguy136]

That sucks on the wiring issues. Those are never fun, especially when it's someone else's shoddy work.

On the tach issue, probably just loose wiring that when you took it apart and put it back together, you tightened it up better.

On the O2 issues, first, what wideband do you have? Did you make sure to put it into O2 simulation by turning the little screw in the back? For example, on an AEM UEGO, it has to be in P4, with the extra blue wire to the o2 sensor input in the ECU.

As to it not going into closed loop, this list might help.

Note:Only ONE of the conditions below must be met in order to put the ECU into Open loop.

• Throttle position too high (varies by RPM)
• Airflow too low (units are tricky, but it's very low)
• Coolant temp < 87F
• The O2 sensor did not switch around 0.5v for over 20 seconds while running in closed loop mode. In that case, the ECU locks itself in open loop mode.

Hope this helps.