1998 Chevy Cavalier, PO480 code, please help if you can

[zieg85]

It is a 1998 Chevy Cavalier with a 2.2L automatic, nothing fancy.  I bought it with a blown engine.  My son rolled his 1998 Chevy Cavalier which was excellent in every way.  They were identical as far as options and drive train.  After the engine/trans was put it and running I now have a PO480 code.  I am at a loss as to what the problem may be.  The other car did not have the code.  I have reset the computer and the code comes back within 10 seconds of starting it up.  The fuses are good and I can remove the fan relay and jump the fan and it will turn on with no problem.  I have to find the issue because it won't pass emissions in order to register the car in my county.  Thanks in advance.

[thirsty]

Zieg, do you still have the parts car and the engine from the new car? I would swap relays and temp sensors if you do.

I'm not 100% sure on this: the a/c might be tied into that circuit too.

[zieg85]

Zieg, do you still have the parts car and the engine from the new car? I would swap relays and temp sensors if you do.

I'm not 100% sure on this: the a/c might be tied into that circuit too.

I guess I could push come to shove however the engine and all its sensors were great before and after the roll over.  I ran the car an hour after it had been rolled to make sure it was all right, the fan came on like it should have and the computer did not have any codes, I checked, before I unhooked the battery prior to the engine removal.  The unknown is the new car...  I have a decent Craftsman code reader so resetting the DTC's aren't an issue.  It has to be one of the connections that would cause the DTC to set, just don't know where to start or which ones have anything to do with the problem.

[VileZambonie]

Zeig,

Here is the diagnostic flow chart, description and test procedure. Let me know if you need help:

CIRCUIT DESCRIPTION
The electric cooling fan is controlled by the Powertrain Control Module (PCM) through the cooling fan relay based on inputs from the following components:



Engine Coolant Temperature (ECT) sensor.
Intake Air Temperature (IAT) sensor.
A/C selector switch.
A/C refrigerant pressure sensor.
Vehicle Speed Sensor (VSS) .
The PCM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay.

The cooling fan relay will be commanded ON when the following conditions are met:



Engine coolant temperature reaches 106°C (223°F) or more.
A/C clutch requested.
Vehicle speed is less than 38 MPH. The cooling fan relay will be commanded ON regardless of vehicle speed when the following conditions are met:
A DTC is set that requests the coolant fan to be ON.
Engine coolant temperature is 151°C (304°F) or more.
A/C refrigerant pressure is high.
The cooling fan may be commanded ON when the engine is not running under a fan Run-On conditions described in the Electric Cooling Fan General Description portion of the service manual.

CONDITIONS FOR SETTING THE DTC


Battery voltage is greater than 9.5 volts.
Coolant fan fault line detects a malfunction for 6 seconds.
ACTION TAKEN WHEN THE DTC SETS


The Malfunction Indicator Lamp (MIL) will illuminate.
The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
A history DTC is stored.
CONDITIONS FOR CLEARING THE MIL/DTC


The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm up cycles without a fault.
The MIL/DTC(s) can be cleared by using the scan tool.
DIAGNOSTIC AIDS


If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or if the Temp light, or temperature gage indicated overheating.
Check for the proper amount of coolant in the system.
If the gage, or light, indicates overheating, but no boil over is detected, the gage or light circuit should be checked. The gage accuracy can also be checked by comparing the engine coolant temperature sensor reading using a scan tool with the gage reading.
If the engine is actually overheating, and the gage indicates overheating, but the cooling fan is not coming ON, the Engine Coolant Temperature (ECT) sensor may have shifted out of calibration and should be checked. Refer to Temperature vs Resistance table.
If the engine is overheating, and the coolant fan is ON, the cooling system should be checked.
TEST DESCRIPTION
Number(s) below refer to the step number(s) on the Diagnostic Table.



The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
The cooling system operation and the coolant level should be checked before determining if any electrical conditions are present causing a cooling system malfunction.
With the engine OFF, the cooling fan motor should not be commanded ON by the PCM.
If the cooling fan motor turns OFF after disconnecting the PCM electrical connectors, the PCM was causing the cooling fan motor to be ON constantly.
A test light that illuminates indicates that the cooling fan motor battery feed circuit is shorted to battery voltage. The cooling fan motor will also remain engaged when the cooling fan relay is disconnected.
Connecting the cooling fan relay battery feed and the cooling fan motor battery feed circuits together bypasses the PCMs control of the cooling fan motor. A cooling fan motor that fails to engage at this point indicates that the malfunction is in the cooling fan motor battery feed circuit, the cooling fan motor or the cooling fan ground circuit.
The battery feed is supplied to the cooling fan relay through the same fuse. No voltage on both circuits would indicate that the fuse is open. Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.
With the engine stopped and the cooling fan relay commanded ON, the PCM should ground the cooling fan relay control circuit. This will also illuminate the test light.
This step determines if the reason the cooling fan motor did not come ON was due to an open battery feed circuit to the cooling fan motor.
The replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM programming and the CKP System Variation Learn Procedure for the Crankshaft Position System Variation Procedure.
If no malfunctions have been found at this point, refer to the DIAGNOSTIC AIDS or additional checks and information.

[zieg85]

Thanks Vile, I really hoped you would respond with your resources.  I will digest this and start the process in the daylight...

[Blazin]

I have had an air bubble in the cooling system fake out the senders and set a code in a Malibu before. Had to back it up onto and embankment, and run it to get the air completely out of the system.
Just a thought.

[zieg85]

I have had an air bubble in the cooling system fake out the senders and set a code in a Malibu before. Had to back it up onto and embankment, and run it to get the air completely out of the system.
Just a thought.

Thanks, I'll back it up on some ramps before I start, makes sense cause you really can't see that it is full and circulating.

[zieg85]

Read on how to bleed the air out of the cooling system... Burped the bleeder on the heater bypass hose, backed it up on ramps and ran it to operating temps so I am pretty sure all the air is out it.  I cleared the DTC and it came back in 6 seconds.  I guess my scan tool isn't good enough to turn stuff on so I couldn't follow the flowchart like I had hoped.  I swapped the PCM's around and while I couldn't get it to idle on its own before it would shut off, it did set the same PO480 code so I put the old PCM back in it.  Connections seems fine with no corrosion.  I did play around with resetting the code while driving it.  The code reader does have freeze frame data capabilities and it did show the speed sensor, temp sensor and rpms at the time the DTC registers.  Again, the fan will come on if I jump the relay.  Any wisdom or should I take it to the experts???

[bd]

If you ground the dark green wire at the relay socket (Ckt 335 in the image Vile posted), does the relay 'click' and fan run?  If it does - qhm the dark green wire between the relay and the PCM.  If not, do you have 12 volts on both red wires (Ckt 542) at the relay socket?  Is it safe to assume that when you bypassed the relay, you did so by jumping the relay socket?  Flip the relay over and compare the terminal numbers on the relay to the diagram - is the socket wired correctly?

[zieg85]

If you ground the dark green wire at the relay socket (Ckt 335 in the image Vile posted), does the relay 'click' and fan run?  If it does - qhm the dark green wire between the relay and the PCM.  If not, do you have 12 volts on both red wires (Ckt 542) at the relay socket?  Is it safe to assume that when you bypassed the relay, you did so by jumping the relay socket?  Flip the relay over and compare the terminal numbers on the relay to the diagram - is the socket wired correctly?

I will check it in the morning.  Both red wires are hot.  I jumped the relay socket with the relay not installed and the fan started.  Any idea what pin the green wire is at the PCM, there is a bunch of them on each plug?

[bd]

You might PM Vile for pin info.  A WAG is pin 54 Connector 2.

[zieg85]

I actually had a good day today for once in that after work I didn't have to collapse from exhaustion...Small update... tracing the dark green wire on the known "good but smashed Cavalier's" wiring to the PCM I've identified the wire pin at the PCM plug(pictured with the custom made finishing nail)...  Wish it wasn't raining so hard or I would check the green car and see if that is the problem.  Stay tuned.

[zieg85]

So happy right now... Replaced the green wire and problem solved.  Wish I would have started at the PCM because that is where I found the crimped green wire.  Need to tidy up the wiring and fix some other issues but the check engine light stays off now...  Thanks BD and Vile  A BUNCH!!!