Question about temp sensor wiring

[Alpha Tweak]

Hello peeps. Got a weird scenario that I need expert advice on. I have a 90 TT 5 spd. A while back I had relocated my PTU to the front & after some hard driving one day the car refused to start up next morning. After a visual inspection I noticed that my fan blade had cut through the harness that goes to the temp sensors up front. I had to splice in a couple of additional pieces of wire (approximately 4 inches or so) in order to reconnect the temp sensor connector harness with the main loom it branches out from. The loom was very brittle & I had to cut through the external wrapping in order to expose enough of the wires so that I could reconnect them again. Problem is I could not tell which wire was which & so I may have spiced them wrong. By this I mean that I may have connected the top wire on the loom to the bottom wire on the sensor harness & vice versa . I had run diagnostic codes before the surgery & sure enough there was a code indicating that the temp sensor circuit was open. After the surgery the code was cleared so I figured that I had in fact connected the wires correctly. My question is would an inverted splice like I mentioned above fool the computer into thinking the circuit is ok & closed thus not throwing a code but in fact cause problems with the mixture & cause the car to run SUPER RICH which is in fact what is happening?

[Alpha Tweak]

Anybody gonna step up & answer this?

[nissanfreak12]

If you relocated the PTU, the fan should have only cut through 3 wires. Have you tried to swap the wires and see what happens. The computer sees it as a closed circuit, so it won't throw a code if it was backwards. But it may not read it correctly or how it should. It could always think the car is running cold therefor running rich. Swap the wires, what could it hurt?

[Alpha Tweak]

If you relocated the PTU, the fan should have only cut through 3 wires. Have you tried to swap the wires and see what happens. The computer sees it as a closed circuit, so it won't throw a code if it was backwards. But it may not read it correctly or how it should. It could always think the car is running cold therefor running rich. Swap the wires, what could it hurt?

Thanks "nissanfreak12". I 've been wanting to do as u suggested but just needed another Z persons advice like yours cause I was scared to burn the sensor or worse the ECU by doing so. When I connect the car to the nissan datascan software via the Blazt usb cable that i have, I'm getting a temperature reading on my laptop so I wonder, is the reading coming from the sensor that goes to the ECU or the one that goes to the gauge?

[nissanfreak12]

As far as I know, that coming from the temp sensor to the ECU, not the one to the dash. You should burn the ECU by being swapped, the worse it will do is throw it in a loop, ie like the sensor is bad. Swap the wires and hook it back up, see what happens. All the sensor is a thermal resistor.

How do you know it is running rich?

[Alpha Tweak]

As far as I know, that coming from the temp sensor to the ECU, not the one to the dash. You should burn the ECU by being swapped, the worse it will do is throw it in a loop, ie like the sensor is bad. Swap the wires and hook it back up, see what happens. All the sensor is a thermal resistor.

How do you know it is running rich?

Guess I can swap the wires then since there is little risk of further damage. However if I am getting temp readings from my datascan software & its getting it via the temp sensor to the ECU, then it seems that it is in fact already connected correctly. I was hoping for a quick fix but at least I can now eliminate the sensor as the problem. Thanks for the feedback "nissanfreak12". The car is running SO rich that it is undrivable. The last 5 times that I have test driven it in order to see if my adjustments have made any difference, It has backfired loudly, won't accelarate smoothly & left me stranded a couple of times. I can smell the fuel from inside the cockpit. I've had the detonation sensor code 34 for a long time but Its never been undrivable like this so I doubt that being in "Safe Mode" is causing this problem. My theory is not that the car is delivering too much fuel, but rather that since I have 2 dead cylinders, there is no spark in those cylinders but the injectors are still dumping fuel into them thus causing this rich condition.
Its not the coilpacks & I have cleaned up the PTU connections & zip tied the connections together since they were loose. The injectors tick as they should & I scraped the pins on the CAS. All the grounding points are tightly screwed down. I wanted to check the PTU itself with a multimeter but I can't get the connectors off & I'm scared of busting them cause then I'll have yet another variable to worry about. I love this car but its kicking my arse.

[nissanfreak12]

Did it cut the wires for the PTU? This could be your issue. How many wires did you have to splice back together?

[Alpha Tweak]

Did it cut the wires for the PTU? This could be your issue. How many wires did you have to splice back together?

Only the 3 wires to the sensors seem to have been severed. But there is a portion of the main loom where it bends into kind of a loop that shows an exposed red wire where the fan blade sliced thru the outer tape of the wiring. Hmmm u may be onto something. I'll take a closer look tomorrow although not sure how to test this without swapping in an entire harness.

[nissanfreak12]

If you have two cylinders not firing, not getting spark, then its either PTU or coil. Could be more but these are the normal culprit. I have heard the coils very rarely goes out. Do you happen to have the old style PTU? There was a recall on this.

Old style will look aluminum with fins on the front.

New style will be a black plastic material on the front.