I have a 1988 Chevy G30 cargo van w/5.7L, 400 auto w/ac. It was a GTE fleet vehicle that I obtained in 1994 w/89,000 mi. It's been a good runner except when something conked out (distributor, coil pick-up, alternator, radiator holed, EGR stuck) which threw codes. It now has 192,000 mi. and lacks the old zip it once had plus it's gas mileage had decreased over the years. I checked out all the vacuum hoses (replaced a few) which helped a little. The coolant temp sensor is the original unit so thought about replacing it due to it's age and being fairly cheap. Mine has the two wire connector pig-tailed into a round terminal that's grounded to the a/c bracket. (it uses a factory terminal like those for the headlamp grounds) My Haynes manual shows those leads should go to the ECM yet this arrangement has never thrown a code all these years.
So my questions are:
1. Was this a quick fix for a faulty ECM back then? GTE was the only one to wrench on this before I got it.
2. I have a new CTS. Should I install it with the same connector?
3. Where did the leads from the CTS go in the OEM harness if I wish/need to rewire it back to normal? I can't tell where they could have been located beforehand.
4. Would I be better off to leave well enough alone?
Thanks for any helpful info!
The ground wire numbered 452 black is spliced with the ground of the Throttle position switch (TPS). The ground continues to the ECM to the smaller plug on the computer and is numbered 452 black wire or 11A on the plug.
If you want to wire it the right way, I would go the local library and check out the wiring of the ECM in the automotive manuals they have just to be sure. Ask the Librarian where the automotive section is and look for the manual for the year and make of your truck.
If you really don't have a problem and want to check it for the proper operation, get yourself a scanner or go to someone who has a scanner and see if the coolant sensor is working properly. If it checks out to be good then don't look for problems and leave it alone.