jpapi68

1999 Camaro LS1 turbo cooling fans stopped working after being parked for 2 weekends while replacing oil pump. Car has 40,000 miles and 1 year old Derale 16925 fans wired into the factory pcm controlled fan wiring, and the connections are not loose or corroded.

I have a cooling temp sensor reading with 5v input into the sensor. Any idea what the resistance across a good sensor should be so i can check that?

I have not been able to get any voltage to the #3 fan circuit (which if i understand correctly controls circuits 1 and 2). Does the car need to be hot and have the PCM sending signal to the circuit to get any voltage? I was checking across pin 30 to 87a and 87 on the relay inputs while the car was cold, key on and was showing no voltage.

The same day after I realized the fans were not working and the car overheated I got check engine lights for:
P0103-Mass air flow (MAF) sensor/volume air flow (VAF) sensor high input - no MAF on vehicle, should have been deleted out by tuner as vehicle is speed density now. No CEL previously.
P0405-Exhaust Gas Recirculation Sensor Circuit A Low - No egr system on car, should have been deleted out by tuner. Never had a CEL before.
P0480-Cooling Fan Relay 1 Control Circuit - may have been because I unwittingly put a 5 pin relay in a 4 pin and a 4 pin in a 5 pin. oops.
P0481-Cooling Fan Relay 2 Control Circuit - may have been because I unwittingly put a 5 pin relay in a 4 pin and a 4 pin in a 5 pin. oops.

Any and all help will be greatly appreciated as I am getting ready to road trip this car to Alaska. Thanks Obama? Is that still a thing?

2xLS1

iTrader: (25)

PCM outputs grounds to turn fans on. They either both run low speed (fan 1 control) or both run high speed (fan 2 control). Get your meter out and troubleshoot the circuit.

jpapi68

I'll do some tracing and get back, thank you for the schematic. I wasn't able to find one specific to my '99. Thank you.

jpapi68

I have 12v at the 40A fuse.

I've got no power to the 10 A mini fuse underhood
​​​with key on. I probed the B8 and C10 on the cooling fan 3 relay circuit ( 85 and 86 slots for the relay) nothing. Go to the red pcm harness, probe both sides of pin 33, a dark blue wire, voltage reads 0. Any suggestions on what to do next?
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jpapi68

Service manager at local Chevrolet suggested replacing coolant sensor. Will update with results.
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jpapi68

Changing the coolant temperature sensor did not rectify the issue.

So very confused now.

jpapi68

Called the dealership, service manager had me ground B1 on the cooling fan relay 1 circuit which did not turn the fans on as he told me it should have.

Might need a new PCM now Will keep updating.

2xLS1

iTrader: (25)

Dealer Service Managers are typically dumb asses about working on vehicles They know how to write up service work orders and assign jobs to mechanics. How is a coolant temp sensor that has 2 terminals that go straight to the PCM going to keep 12V from getting to a fuse in the fuse box. Going by this you must have an open between the fan maxi fuse and the fan mini fuse.

jpapi68

I'm getting 0.2 ohms across the wire from maxi to mini fuse. I did notice that at some point in my testing the maxi fuse had blown. Going to warm the car up again .

jpapi68

So yeah, the sensor fixed. The fuse had blown without me noticing, that's why the fans did not come on after i replaced the sensor. Don't I feel stupid.
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2xLS1

iTrader: (25)

Your post #4 said you had 12V at the maxi and 0V at the mini. That is what I was going on.