Circuit Description
The tire inflation monitor (TPM) system uses the EBCM, wheel speed sensors, class 2 serial data messages, and instrument cluster in order to perform the system functions.
The EBCM contains the software to perform the system monitoring functions. The EBCM uses wheel speed data obtained from the wheel speed sensors to detect relative rotational differences. Any ABS/TCS system activity causes the EBCM to temporarily suspend the tire inflation pressure system functions.
Conditions for Running the DTC
The vehicle speed is between 24-145 km/h (15-90 mph).
Conditions for Setting the DTC
One of the following conditions occur:
| • | The EBCM detects a tire pressure difference of 82 kPa (12 psi). |
| • | DTC C1254 sets. |
| • | Loss of battery positive voltage (B+) at the EBCM. |
| • | A battery disconnect or a low battery voltage condition. |
Actions Taken When the DTC Sets
The Instrument Panel displays the LOW TIRE PRESSURE indicator.
Conditions for Clearing the DTC
The condition for the DTC is no longer present and you have performed the tire inflation monitoring reset function.
| • | By using the scan tool Clear DTC function. |
| • | A history will clear after 100 ignition cycles. |
Diagnostic Aids
Any of the following conditions can cause this DTC.
| • | One or more of the vehicle's tires is under inflated. |
| • | One or more of the vehicle's tires is over inflated. |
| • | The tire pressures have been altered without resetting the TPM. |
| • | When tires have been rotated or any tire changed you must reset the TPM. |
| • | The tires are different then the original equipment manufacturer (OEM). |
| • | Loss of battery positive voltage (B+) at the EBCM. |
| • | A battery disconnect or a low battery voltage condition. |
| • | Moisture in wheel speed sensor connector. |
| • | Rough or slippery road conditions. |
| • | A suspension condition (i.e. the vehicle out of alignment). |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the TPM Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC C1245 is current? | -- | Go to Step 3 | Go to Diagnostic Aids |
Since most occurrences of this DTC are caused by low tire pressure, review the TPM system with the customer to verify the conditions under which the DTC set. Did vehicle operation cause this DTC to set? | -- | Go to Step 5 | Go to Step 4 | |
4 |
Does the DTC reset as a current DTC? | -- | Go to Diagnostic Aids | System OK |
5 | Inspect the tire pressures and adjust if needed. Perform the tire inflation monitoring reset if tire pressures were adjusted. Refer to Tire Inflation Monitor Resetting for service procedure. Did you complete the repair? | -- | System OK | -- |
