oilcan

97 cavalier code p0480 cooling fan the fan will not operate engine will over heat have checked the fan relay it is ok by using a jumper wire the fan will run I have also replaced the coolant temp sensor checked continuity of wires from ect to pcm all check out ok only thing I can think of is a faulty pcm have no scan tool to do any extensive testing would appreciate any and all help

EinST

Welcome to the forum. Have you taken the PCM connector C2 off and verified a battery voltage on pin 54 (fan relay control circuit)? Also, measure the resistance across PCM connector C1, pin 54 and C2, pin 27 (ECTS circuit), with both connectors off the PCM?

oilcan

thanks for the info I will check that today should voltage be 12 volts or will it be less what would the resistance be between terminals I do have a digital multi meter one other thought does anyone know if pcm from 2000 sunfire same engine only auto instead of man trans will interchange this is starting to tick me off {1} neither plug on pcm states c1 or c2 found some info on another site that refered to c2 as being black.{2} pin#54is what pin fromwhere as again nothing to indicate where #s start from,went to local auto parts store bought Haynes manual wiring diagrams in it are of little value as they dont show any pin #s and only have a wire # as high as 21 if pin #54 is 7th pin from centre on black plug there is only 1. volts

oilcan

EinST

I had assumed certain things, based on your first post. The connectors are just the usual 2x40 variety and goes like pins 1-20, 21-40 left to right on bottom and then 41-60, 61-80, again left to right, on top. You may see the same pictured upside down.

The DK GRN wire from the fan relay control coil terminates at connector C2, pin 54. The other side of the control coil gets the battery voltage. The PCM then grounds it to energize the relay. With the connector off, the circuit floats and thus it should read near battery voltage on connector C2, pin 54.

On connector C1, pin 54 (YEL wire) and C2, pin 27 (BRN wire), I was wondering if there was anything funny going on like open or excessive resistance across the ECTS which will be interpreted as artificially low temperatures.

oilcan

my main concern was which connector was c1 or c2,I did get a wiring diagram that pointed that out and shows pin #s only not sure if they are in numerical order.I don,t recall any pins showing full battery voltage however I will recheck I did check continuity on wires for ects continuity was good I replaced ects I might not get back to this until weekend as tractor trailer is waiting to go to work. will let you know how it goes and thanks again

greatobd2

Have you taken the PCM connector C2 off and verified a battery voltage on pin 54 (fan relay control circuit)?