skyhawk50

Searched tech forum for an answer, nothing found. Here's the issue. As soon as engine in my 92 base LT1 is started, both cooling fans come on, digital temp shows 142 degrees F immediately, SES light on immediately. Using my FSM, it appears that if the ECM doesn't detect a good fuel pump relay, it kicks the fans on and allows fuel pump to run as long as oil pressure detected. Does his sound correct ? Anything else I should be checking? Digital coolant sensor ( the one in water pump ) has been replaced, didn't correct problem. Where is the fuel pump relay located? Any ideas ?

STL94LT1

It still sounds like a coolant temp sensor issue. Are you sure you purchased the correct CTS?

scotth48

Putting my 93 LT1 back together and the primary fan comes on when key is on. Upon looking at fsm I came across a possible cause. Since the Freon has not been installed yet it said that the fans rely upon information including that from the A/C. If it has a low amount of Freon in the system it may cause the fans not to operate correctly. It may be something to check out if a/c hasn't been serviced lately.

Cliff Harris

If the ECM thinks the AC is on it will turn on the fan. This is controlled by a pressure switch in the AC lines. My recollection is that it's "backwards" from what you would expect. If you unplug the connector the fan will run all the time. That connector needs to have the pins connected together to tell the ECM that the AC is NOT on.

If you follow the AC lines you will find two pressure sensors next to each other. The one with the smaller connector is the fan control switch.

skyhawk50

Hopefully Napa sold me the correct cts. I'll check the AC pressure switches. The AC hasn't worked for about a year. It's not a high priority at the moment.

skyhawk50

Update. verified that the cts is correct, replaced the pigtail to the plug. no luck. the scenario is as follows : 142 degrees shows on digital temp at start up. shows 142 degrees even with harness unplugged. BOTH fans on at start up. AC hasn't worked for at least 2 years with no issues before. check engine light on, shows a code 14. tried resetting, comes back on. is it possible that the harness ( 2 wires) from the ecm to the cts could be rubbed through or shorted ?? just asking

STL94LT1

A simple continuity test will answer your question.

WVZR-1

Here are the Delphi specs for the CTS. Check the CTS out of the box and then set about checking the circuit after you confirm the correct operation of the CTS:

http://www.pe-ltd.com/joomla/images/...olant_temp.pdf

Here's the more frequently mentioned approx. values:

F / C / Ohm value

210 / 100 / 185
160 / 70 / 450
100 / 38 / 1800
70 / 20 / 3400
40 / 4 / 7500
20 / -7 / 13500
0 / -18 / 25000
-40 / -40 / 100700

skyhawk50

Problem solved. I ran a jumper wire from the yellow wire on the cts to the yellow wire on the gray plug of the ecm ( thank you fsm) Started car, no cooling fans running, digital readout showed 80 degrees F. Left idle, watched temp rise normally, still no fans and no sel light. Appears to be a faulted wire somewhere in the harness. New wire run, old wire left in place.

Ok car, what's next ? I know before the weekend another issue will pop up. A 22 year-old car is just dying for attention.

Now, back to my 89 C4 and get the front brakes sorted out

I'm glad neither is a daily driver.