RogerStout

iTrader: (1)

I noticed my car was running a little hot 190 with a 160 thermostat.

I replaced the thermostat thinking it might be faulty. No joy.

Next I tested the high fan relay and was able make the high fans come on by grounding the signal wire (dark blue) to the chassis.

Pulled C2 from the PCM and grounded pin 33 and high fans come on.

Hp tuners connected using the scan tool to activate high fan does nothing. Low fan comes on but activating high fan does nothing in the scanner.

I am running out of ideas here. Any advice anything else I can test?

GaryDoug

First, 190 isn't that hot. The thermostat regulates the minimum temperature, not the maximum. Your 160 thermostat keeps the engine to AT LEAST 160, not under 160. Is the PCM programmed to have the fans on at lower than normal temperatures (226F low speed, 234F high speed)?

Second, grounding pin C2.33 doesn't necessarily turn on both fans on high speed. It turns on the passenger side fan only on high speed if the other fan isn't already on. Only if the driver side fan is already on (via relay 1), will both fans will be on and at high speed. This is how it works: Relay 1 on=both fans on low speed, Relays 2 and 3 on=passenger side fan on high speed, Relays 1,2 and 3 on=both fans on high speed.

Have you monitored the engine temperature using the scan tool? The temperature might read different from the gauge if the gauge has a defect.

RogerStout

iTrader: (1)

Yes I have 190 and at times 200, the car has never been this hot in the past. The tune calls for the fans to come on at these points.

Fan 1 on 180
Fan 1 off 175

Fan 2 on 187
Fan 2 off 180

At a 190 both fans should be on high. In the scan tool I can not even turn on the high setting at all. All relays have been testing and are working properly. Low settings can be activated via scan tool. High does nothing. Turning on AC also does not activate high fans.

GaryDoug

Look close to see if both fans are actually running when the temp is 200. One fan on high speed is fairly loud and you might miss seeing that one isn't on. Again I will ask, is the 200 reading coming from the gauge or from the scantool? The gauge may be off by at least 10 degrees.

Turning on the AC only turns the fans on to low speed (relay 1). Only the PCM temperature reading determines whether they go to high speed or not.

RogerStout

iTrader: (1)

Yes the temp number is from the scan tool. When I activate fan low both fans are running on low and I can hear the relay click (scan tool) leaving fan 1 on and clicking fan 2 (high) changes nothing. still runs on low no relay clicks. grounding pin 33 activates high.. its loud. I start the car and I can not hear fan low but have a visual conformation.

Here is one odd thing I have noticed. If I activate fan 1 (hp tuners) then fan 2 then shut off fan 1 it continues to run low. When I shut off fan 2 then the fans are off. Activating fan two alone does nothing. Not clicks no fans..

its says fan 2 in hp tuners but its fan high.

RogerStout

iTrader: (1)

Tonight I am going to test continuity on pin 33. If the PCM is actually sending ground to the circuit I should see continuity when fan 2 is activated in Hp Tuners Scan tool. I know from C2 to the relays is fine and the fans are fine so this only leads me to believe its a connection problem or bad PCM.

RogerStout

iTrader: (1)

Bad PCM, replaced it all is good.

GaryDoug

Be careful to avoid connecting ground or 12v to any output pin of the PCM to test anything. Some pins can tolerate it and others cannot. I fried a driver module once by connecting 12v to the fuel pump relay output. Luckily I found a cheap V6 pcm with the same driver module and replaced it for $15.

ws6man29

iTrader: (1)

Good deal!

Paul Bell

iTrader: (9)

Glad you've fixed it.

Just for reference, (in Corvettes and LS1 F-Bodies) fan 1 places both fans on low speed (in series). Fan 2 places both fans on high speed (in parallel).

Unless you're running HOT, high speed is rarely achieved. Engaging the AC will also get high speed on sooner.