Cooling Fan and Ignition Issue
10-27-2014, 12:04 PM
#1
Cooling Fan and Ignition Issue Hello All,
I searched and couldn't find a good answer, so here goes...
The two small fans on my 2002 SS continue to run after I turn the car off (car off, keys out of the ignition, etc.). Temps are all right in line -- never see anything over 195*.
Interestingly enough, I've found that if I put the key back in the ignition and turn it forward (without actually starting the car), the fans will turn off. Turn the key off, take it out and you're good to go.
Any idea what would cause this?
One other symptom worth mentioning, is the fact that I do get the occassional stumble on idle and the car will cut off. Not sure if it's related, however I guess it might be something electrical that ties all of this together.
I searched and couldn't find a good answer, so here goes...
The two small fans on my 2002 SS continue to run after I turn the car off (car off, keys out of the ignition, etc.). Temps are all right in line -- never see anything over 195*.
Interestingly enough, I've found that if I put the key back in the ignition and turn it forward (without actually starting the car), the fans will turn off. Turn the key off, take it out and you're good to go.
Any idea what would cause this?
One other symptom worth mentioning, is the fact that I do get the occassional stumble on idle and the car will cut off. Not sure if it's related, however I guess it might be something electrical that ties all of this together.
10-27-2014, 04:14 PM
#3
are the fans off when engine is running, then you turn engine off and fans start running?
or does it only happen if fans are running while engine is running, then you shut engine off and fans continue to run?
fans only run on low speed, commanded by PCM, when engine coolant is above 226°F or the air conditioning is turned on. normally the fans turn off when engine is turned off, but when there is an overheat condition where coolant temp is above some high number like 260° or 280° the fans will continue to run when engine is off for some amount of time- most likely not the case since you said your temps not above 195.
way the fan relays work is there's 3 of them, and from 2 of them is a wire going to the pcm. a blue wire and a green wire, ground one and fans turn on low speed.
ground both and fans high speed.
green wire pcm pin 42 - just this one grounded equals low speed.
blue wire pcm pin 33.
the circuit/switch within the pcm connects these wires to ground to control the fans. so if your relays are not sticking which i don't think is likely, my guess is when engine is turned off the pcm is continuing to latch that green wire to ground, until you power cycle the pcm with ignition key and is when it resets. so possible pcm malfunction if not relay malfunction. use a multimeter and probe the green wire and see if it has 0 volts on it when engine off which means the fans are running, it should have 12v on it if the pcm is not grounding it.
or does it only happen if fans are running while engine is running, then you shut engine off and fans continue to run?
fans only run on low speed, commanded by PCM, when engine coolant is above 226°F or the air conditioning is turned on. normally the fans turn off when engine is turned off, but when there is an overheat condition where coolant temp is above some high number like 260° or 280° the fans will continue to run when engine is off for some amount of time- most likely not the case since you said your temps not above 195.
way the fan relays work is there's 3 of them, and from 2 of them is a wire going to the pcm. a blue wire and a green wire, ground one and fans turn on low speed.
ground both and fans high speed.
green wire pcm pin 42 - just this one grounded equals low speed.
blue wire pcm pin 33.
the circuit/switch within the pcm connects these wires to ground to control the fans. so if your relays are not sticking which i don't think is likely, my guess is when engine is turned off the pcm is continuing to latch that green wire to ground, until you power cycle the pcm with ignition key and is when it resets. so possible pcm malfunction if not relay malfunction. use a multimeter and probe the green wire and see if it has 0 volts on it when engine off which means the fans are running, it should have 12v on it if the pcm is not grounding it.
10-27-2014, 04:35 PM
#4
Awesome info above -- thanks so much for your help.
I'm not particularly adept at the hands on part of solving these issues, however I'll first check to see if the fans are "off then turning on" or "on and continuing to run after the car is turned off" and will then pull out the multimeter for step two (if necessary).
I'm not particularly adept at the hands on part of solving these issues, however I'll first check to see if the fans are "off then turning on" or "on and continuing to run after the car is turned off" and will then pull out the multimeter for step two (if necessary).
10-27-2014, 08:16 PM
#5
for probing that green & blue wire, on the passenger side is the PCM and the wiring harness comes out from there. on the passenger side top of wheel well are two separate wire bundles each having a disconnect plug. in one of them, green wire is pin J in connector and blue wire is pin H. the black or dark brown plastic of the connector has A B C D... marked on each pin,
When engine is off if your fans are still running, you can just undo that one plug.
if your fans go off then that proves the PCM was grounding the green wire because you just broke that connection. you technically don't need a meter to probe wires.
When engine is off if your fans are still running, you can just undo that one plug.
if your fans go off then that proves the PCM was grounding the green wire because you just broke that connection. you technically don't need a meter to probe wires.
Last edited by 1 FMF; 10-27-2014 at 08:22 PM.
10-28-2014, 10:28 AM
#6
for probing that green & blue wire, on the passenger side is the PCM and the wiring harness comes out from there. on the passenger side top of wheel well are two separate wire bundles each having a disconnect plug. in one of them, green wire is pin J in connector and blue wire is pin H. the black or dark brown plastic of the connector has A B C D... marked on each pin,
When engine is off if your fans are still running, you can just undo that one plug.
if your fans go off then that proves the PCM was grounding the green wire because you just broke that connection. you technically don't need a meter to probe wires.
When engine is off if your fans are still running, you can just undo that one plug.
if your fans go off then that proves the PCM was grounding the green wire because you just broke that connection. you technically don't need a meter to probe wires.