2002 impala cooling fans

[claytonduk]

I'll retest those now. puttin 'er back together......

[claytonduk]

another thing I never mentioned. The wiring harness to the CTS had another connector on top of the engine so I've been disconnecting it from there because of easier access. There are no other wires other than from the CTS . Does this section have to be tested for cont?

[bozr]

It may not matter as long as fan 2 is still coming on but I would disconnect at the CTS for the last few tests to be sure.

[claytonduk]

all back together . engine running cts removed. I did check cont on the section of cable going to the cts and there was cont on both wires. I checked volts between 85 and 86 on fan2 which was 14.35. between 85 and 86 on fan 1 the volts started out at 14 and steadily dropped down to 2 or so. 85 on both sockets to ground was 14.35. ther was no cont to ground on both 86 sockets . sounds like a ground issue

[bozr]

There would be no continuity to ground on 86 because it's hot. Does your meter still work.

Fan 1 relay socket
Test for voltage from 86 to ground?
Test for continuity from 85 to ground? (Engine running CTS removed)

[claytonduk]

85 on all 3 relays has 12.35 volts to ground with engine off and 14.55 volts to ground with engine on cts removed. 86 on fan2 and mode relay had a 37 reading for cont. fan1 socket 86 had no cont to ground. 85 is hot 86 is ground.

[bozr]

Ok, that helps. Are the socket terminals marked with B8, C8, C10 and B10?

What's missing is the ground signal from 86, without that, relay 1 doesn't energize. Since you have already tested continuity to the connector the fault points to the PCM.

Before you get a replacement PCM you may want to take it to the dealer. The fans can be commanded on with their scan tool to be certain it’s a bad module.
Also, I'm not sure, a replacement PCM may need to be programmed to your VIN. Someone here might have more info on that.

[claytonduk]

ther are no markings on the sockets . the relay itself has 30,85,86,87. I still haven't tried replacing the mode relay . But you did say that was good .

[claytonduk]

also is there a way to check ground from pcm to relays like I did for cont from pin 6 on the pcm to socket 85?

[bozr]

You can jumper the fan1 relay at sockets 30 and 87 with the engine off. Both fans should come on in low-speed mode. That would test the fan grounds.

The ground that you don't have is the one from the PCM that energizes the coil in relay1 and then connects 30 and 87.

[claytonduk]

can I test the ground from the pcm like I did with pin 6 to socket 85?

[bozr]

Pin 6 to fan1 socket 86 was the ground connection to the PCM.
You already tested the continuity in the wire going to the PCM, right?

The PCM controls the ground to socket 86.

[claytonduk]

sorry yes that was continuity from pin 6 of pcm to socket 85 of fan 1 relay and it was ok.

[claytonduk]

oh yeah I went to autozone and got a new mode relay . I was going to put it in at the store but didnt have plyers to take the old one out. check engine light was still on but as I was driving the check engine light went out. So when I got to my next destination I kept the car running and disconnected the CTS and still only fan 2 came on . I shut the car off and when I started it again within a few miles the check eng came on again. when I got home I swapped the old mode relay with the new one and still only fan2 came on. oh well it was worth a try.

[claytonduk]

hey bozr....remember how you had me jump 30 and 87 with a small wire? Is there any way I can jump the terminals to get the check engine light to go off long enough to get it to pass inspection?