1990 Civic Si running a D16z6, converted to obd1 using a Rywire engine harness and chassis specific subharness, connected to a P28.

All tests are Key On Engine Off. All sensors are stock. Grounds are clean.

I'm getting higher voltage then I should at my stock TPS.

I'm getting 7.29v between (+)Yellow and (-)Green. My understanding is that the yellow wire should always read 5v. When I ground the Yellow wire to the battery's ground I also get the same reading, 7.29v.

When I attempt to calibrate my TPS I can rotate the TPS sensor to achieve .50v at Closed Throttle. When I go to Wide Open Throttle it is not possible to achieve the desired 4.5v, thanks to the excessive voltage.

Would the excessive voltage cause a rich condition, as I am running rich. Any idea what would cause this?

For comparison I also tested the MAP's voltage, which also is off.

Yellow/Red + body ground = 7.37v. Should be 5v
Yellow/Red + Green/White = 7.38v. Should be 5v
White + Green/White = 5.30v Should be 5v, looks acceptable.

Thanks in advance for sharing your expertise.

 

Sounds like you have a bad resistor in the ECU. Do you have another ECU to test with? Any OBD1 ECU should work to test voltages.

 

I tried another obd1 ecu, a PO8, it produced the same results. I also removed the top and bottom of each ecu and looked for burn marks. Both look clean.

While testing the voltage on the ECT sensor, using the PO8 I noticed the voltage slowly climbed.

Any ideas?

No CEL's

 

I see this a lot when the thermostat ground is loose or corroded, or when you have a bad ground wire that's causing extra resistance.
Even Rywire harnesses can have defects, so if you continue to have this problem after cleaning all your grounds & plugs and checking for kinks or broken insulation, you'll probably have to replace your harness(es).

 

I think it's in my nature to over think stuff.

After spending hours reading electrical schematics and researching online, I returned to the garage. I started sniffing my Main Relay, then went all over the fuse boxes, reseating and testing. I checked my grounds again, and finally returned to the engine harness. No voltage change. Scratching my head, I decided to get a simple reading of the battery's voltage, it was near 19v!

I didn't know whether to laugh or cry. I assumed my voltage regulator had been malfunctioning, overcharging the battery, and thus, overwhelming my electrical system with juice. I decided to bleed off the charge by turning on the lights and hazards. As I watched with my trusty multimeter, I noticed the lights dim the closer the read out got to 12v. How could this be? I ran inside the house, ripped the smoke detector off the ceiling, tore the 9volt battery out and probed the terminals...

Needless to say, my multimeter was inaccurate. Harbor Freight was having a sale on meters, $6.97. Now my TPS is properly calibrated, and reference is at 5v.

And the moral of the story, when it comes to troubleshooting electrical systems, test your tester before doing anything.