C0077

C0077- LOW TIRE PRESSURE

For a complete wiring diagram Refer to Diagrams/Electrical.


- When Monitored:
Continuously.

- Set Condition:
A low pressure condition will exist when the tire pressure falls below or is equal to the low pressure threshold value as specified for the vehicle.







Diagnostic Test


1. DTC STATUS
NOTE: If vehicle is equipped with "Light load" reset switch make sure tire pressure matches switch position. Vehicles with a Supplemental Tire Pressure Information Label will have a "Max Load Tire Pressure", and "Light Load Tire Pressure". If the incorrect Placard Values have been programmed, update the Placard Pressures under "Miscellaneous Functions" for the "WCM" and follow the procedure.

NOTE: If the incorrect Placard Values were programmed into the WCM/SKREEM, a DTC could be set. Before continuing with any TPM diagnostic test, using the scan tool, check that the correct Placard Values have been programmed in to the module.

NOTE:
If the following conditions are present:

- Low Tire Pressure DTC

- Tire Pressure Sensor Internal DTC

- Spare Tire is not equipped with a Tire Pressure Sensor

- Spare Tire is currently on the vehicle

Repair the tire and place it back on the vehicle.

Test drive the vehicle.

If the DTC(s) reset continue with the diagnostic procedure.


Turn the ignition on.
With the scan tool, select View DTCs in the Wireless Control Module (SKREEM).
Is the DTC status at this time?

Yes


- Go to 2


No


- Go to 5



2. LOW TIRE PRESSURE
NOTE: If vehicle is equipped with "Light load" reset switch make sure tire pressure matches switch position.


NOTE: The DTC can be caused by many different factors and might not be a sensor/transmitter or a WCM (SKREEM) fault. Interference from other elements will over power the sensor/transmitter RF frequency making erratic operation to the TPM system. Check the vehicle for aftermarket accessories that could compromise the RF frequency signal before diagnosing the TPM system.


NOTE: Seasonal temperature changes will affect tire pressure, and may have caused the tire pressure to fall below the low pressure warning threshold. Tire pressure should always be set based on cold inflation tire pressure (placard). This is defined as the tire pressure after a vehicle has not been driven for more then 3 hours, and in outside ambient temperatures.

Perform a "WCM ECU Reset" under "Miscellaneous Functions" for the "WCM/Wireless Control Module" menu item.
Inflate all tire pressures to the recommended cold inflation tire pressure and wait 2 minutes. The Tire Inflation Pressure (Placard) label is usually located on the Driver's B-pillar.
With the scan tool, clear DTCs in the Wireless Control Module (SKREEM).
Test Drive the vehicle for a minimum of 10 minutes with vehicle speed greater than 15 m.p.h. (24 km/h).
Use a TPM-RKE Analyzer tool 9936 to scan each tire pressure sensor, and make sure the Sensor IDs matches what is programmed into the WCM. The Sensor Identifications are located under "Data Display" for the "WCM Wireless Control Module". If the sensor IDs does not match, following the programming steps outlined in the diagnostic scan tool for "Program Tire Sensor ID w/TPM Tool" under "Miscellaneous Functions" for the "WCM/Wireless Control Module" menu item.
With the scan tool, select View DTCs in the Wireless Control Module (SKREEM).

NOTE: When scanning a sensor with a TPM-RKE Analyzer 9936 , replace the TPM sensor if the results show a "Damaged Accel", "Damaged Temp", or "Damaged Press".

Does the DTC reset or is the status Active for this DTC?

Yes


- Go to 3


No


- Go to 6



3. TIRE PRESSURE SENSOR
NOTE: Before continuing, ensure the tire is free from any leaks or damage that would cause a low tire pressure condition. If a problem is found, repair as necessary and retest.

With the scan tool, go under "Data Display" for the "WCM Wireless Control Module" and find the compensated tire pressure values. Located underneath each Sensor Identification locations. If any compensated tire pressure values are equal or lower then the Tire Low Pressure Threshold. The corresponding TPM sensor needs to be located and replaced.

NOTE: The following tests are used to locate the Tire Pressure Sensor/Transmitter that is setting the low pressure fault. If the tires have been rotated, the Tire Pressure Sensor/Transmitter are no longer in sequence from the factory. Faults are linked to the sensor/transmitter IDs. You MUST locate the correct Tire Pressure Sensor/Transmitter that set the fault before continuing. Use one or more of the following methods below.

METHOD 1: Use a TPM-RKE Analyzer tool 9936 to scan each tire pressure sensor. If a suspected sensor has been located, lower the tire pressure to 20 PSI, wait for 2 minutes, and check the scan tool for changes to any compensated tire pressure values.
If there was a pressure change to any compensated tire pressure values, check to make sure that the TPM-RKE Analyzer is set correctly, and repeat the process on each wheel on the vehicle until the faulty Sensor/Transmitter has been identified.

NOTE: When scanning a sensor with a TPM-RKE Analyzer 9936 , replace the TPM sensor if the results show a "Damaged Accel", "Damaged Temp", or "Damaged Press".

METHOD 2: Starting with the left front wheel, deflate the tire to 20 PSI, wait 2 minutes, and check the scan tool for changes to any compensated tire pressure values.
If there was a pressure change to any compensated tire pressure value, repeat this process on each wheel on the vehicle until the faulty Sensor/Transmitter has been identified.
Has the malfunctioning/faulty TPM sensor been located?

Yes


- Replace the Tire Pressure sensor.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test


No


- Go To 4



4. WIRELESS CONTROL MODULE
Replace the Wireless Control Module (SKREEM).
With the scan tool, read WCM/SKREEM DTC(s).
Drive the vehicle for a minimum of 10 minutes while maintaining a continuous speed above 15 mph (24 km/h). During this time the system will learn the sensor IDs.
Are there any DTC(s) present?

Yes


- Repair not complete, Diagnose and repair the DTC(s).
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test


No


- Repair is complete.



5. INTERMITTENT TIRE PRESSURE SENSOR DTC
The conditions necessary to set this DTC are not present at this time.
Refer to any Technical Service Bulletins that may apply to this condition.
With the scan tool, clear DTCs in the Wireless Control Module (SKREEM).
Test Drive the vehicle for a minimum of 10 minutes with vehicle speed greater than 15 m.p.h. (24 km/h).
With the scan tool, select View DTCs in the Wireless Control Module (SKREEM).
Does the DTC reset or is the status Active for this DTC?

Yes


- Repair as necessary.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test


No


- Test complete.



6. LIGHT LOAD RESET SWITCH
The "Light Load" reset switch will allow the driver to switch between the max load inflation pressure (cold) low pressure warning threshold and the light load inflation pressure (cold) low pressure warning threshold.
Is this vehicle equipped with a Light Load Reset Switch?

Yes


- Go To 7


No


- Go To 5



7. LIGHT LOAD RESET SWITCH LED LAMP
After a WCM ECU Reset, the WCM should be at the Light Load Configuration.
Is the Light Load Reset Switch LED ON?

Yes


- Go To 8


No


- Go To 12



8. LIGHT LOAD RESET SWITCH LED LAMP TEST
Press the LIGHT LOAD RESET switch.
Did the Light Load Reset Switch LED Turn OFF?

Yes


- Go To 5


No


- Go To 9



9. LIGHT LOAD RESET SWITCH LED CCN TEST
Go to "Tire Pressure Load Switch Pressed" under "Miscellaneous Function" in the "CCN - Cabin Control Node".
Start the actuation by pressing the "SET" button.
Did the Light Load Reset Switch LED Turn OFF?

Yes


- Stop the actuation. Replace the Light Load Reset Switch
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test


No


- Stop the actuation. Go To 10



10. LIGHT LOAD RESET SWITCH LED CCN TEST
Go to "Tire Pressure Load Switch Indicator" under "Miscellaneous Function" in the "CCN - Cabin Control Node".
Start the actuation. On the next screen pick "False"
Did the Light Load Reset Switch LED Turn OFF?

Yes


- Stop the actuation. Go to 4


No


- Stop the actuation. Go to 11(Repair the Short to voltage on the LED circuit, or replace the CCN)



11. SHORT TO GROUND ON LIGHT LOAD SWITCH LED CIRCUIT
Turn ignition off.
Disconnect the "Light Load" reset switch connector.
Disconnect the CCN.
Measure the resistance of the G561 circuit in the "Light Load" reset switch connector to ground.
Was there a short to voltage?

Yes


- Repair the G561 circuit for a short to ground.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test


No


- Replace the CCN.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test



12. LIGHT LOAD RESET SWITCH LED CCN TEST
Go to "Tire Pressure Load Switch Indicator" under "Miscellaneous Function" in the "CCN - Cabin Control Node".
Start the actuation by pressing the "True" button.
Did the Light Load Reset Switch LED Turn ON?

Yes


- Stop the actuation. Go to 4


No


- Go To 13



13. WCM / LIGHT LOAD SWITCH / WIRING TO LED CKT
Turn off the ignition.
Disconnect the "Light Load" reset switch connector.
Disconnect the CCN.
Measure the resistance of the G561 circuit between the "Light Load" reset switch connector and the CCN connector.


Is the resistance below 5 ohms?

Yes


- Go to 14


No


- Repair the open circuit.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test



14. F504 IGNITION RUN CIRCUIT
Turn ignition on.
Using a 12-volt test light connected to ground, check the F504 circuit.
Does the test light illuminate brightly?

Yes


- Go to 15


No


- Repair the open circuit.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test



15. SWITCH
Turn ignition off.
Reconnect the "Light Load" reset switch connector.
Using a jumper wire jump the G561 circuit to ground at the CCN harness connector.
Turn ignition on.
Does the "Light Load" reset switch LED turn on?

Yes


- Go to 16


No


- Replace the "Light Load" reset switch.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test



16. LIGHT LOAD RESET SWITCH LED CCN TEST
Go to "Tire Pressure Load Switch indicator" under "Miscellaneous Function" in the "CCN - Cabin Control Node".
Start the actuation. On the next screen press the "true" button.
Did the Light Load Reset Switch LED Turn ON?

Yes


- Stop the actuation. Replace the WCM
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test


No


- Stop the actuation. Replace the CCN.
- Perform the TPM verification Tire Pressure Monitor (TPM) Verification Test