Circuit Description
Tire Inflation Monitor (TIM), also known as Tire Pressure Monitor (TPM), is a unique feature for this vehicle. The TIM system will notify the driver when an urgent LOW inflation pressure condition is present in one of the vehicle's tires so that the driver can quickly perform the needed maintenance. The Body Control Module (BCM) receives a momentary ground signal from the Tire Inflation Reset Switch when the customer or technician presses the reset switch (located in the fuse block). The tires should always be set at the correct pressure before the reset switch is pressed. The EBCM/EBTCM will then send a Class 2 message to the instrument panel (IP) to turn off the LOW TIRE Indicator, and the TIM system will go into the Autolearn mode. The Autolearn mode will then relearn the vehicle tires. The TIM system consists of the following four components:
| • | The 4-wheel speed sensors for gathering wheel speeds |
| • | The TIM software located in the EBCM/EBTCM (if equipped) |
| • | The reset switch for resetting the TIM system |
| • | The LOW TIRE indicator |
Conditions for Setting the DTC
A DTC C1245 can be set any time the TIM system detects a tire pressure difference of 10 psi between the tires on the same axle. This DTC will also be set if DTC C1254 (Abnormal Shutdown Detected) occurs. If the vehicle has a flat tire, the EBCM/EBTCM will set this DTC. If the vehicle has a flat tire and a compact spare is used, the LOW TIRE indicator will still be turned ON because of the difference of tire size (even if the reset switch is pressed).
Action Taken When the DTC Sets
A Diagnostic Trouble Code (DTC) is stored in the EBCM/EBTCM for the TIM system if a malfunction occurs. The Low Tire warning indicator will be turned ON.
Conditions for Clearing the DTC
A history DTC will clear after 100 consecutive ignition cycles if the conditions for the malfunction are no longer present.
All repairs are completed, tires are inflated to the proper psi, and the TIM reset switch is pressed.
Diagnostic Aids
| • | Possible causes for DTC C1245 are as follows: |
| - | One of the vehicle's tires is under inflated. |
| - | One of the vehicle's tires is over inflated. |
| - | The tire pressures have been changed without resetting the TIM system. |
| - | The vehicle tires have been rotated or changed without resetting the TIM system. |
| • | You must conduct a thorough inspection of the wiring and connectors. Failure to carefully and fully inspect the wiring and the connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. Inspect all of the circuitry that may cause the intermittent complaint for the following conditions: |
| - | Broken wire inside the insulation |
| - | Backed out terminals |
| - | Improperly formed terminals |
| - | Damaged terminals |
| - | Physical damage to the wiring harness |
| • | If an intermittent malfunction exists refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | |
Using a Scan Tool, check for ABS Diagnostic Trouble Codes (DTC). Refer to Scan Tool Diagnostics in Antilock Brake Systems for more information. Is DTC C1254 present and current? | -- | Go to Step 3 | Go to Step 4 | |
3 | Go to DTC C1254 Abnormal Shutdown Detected in Antilock Brake Systems. Is the action complete? | -- | System OK | -- |
4 | Using a Scan Tool, clear the ABS DTC(s). Refer to Clearing DTCs in Antilock Brake Systems. Does the DTC reset as a current DTC? | -- | Go to Step 5 | Go to Step 6 |
5 | Replace the Electronic Brake Traction Control Module (EBTCM). Refer to Electronic Brake Control Module/Electronic Brake and Track Control Module Replacement in Antilock Brake Systems for service procedure. Is the repair complete? | -- | System OK | -- |
6 | Refer to Diagnostic Aids for additional information regarding the operation of the Tire Pressure Monitoring System. Is the action complete? | -- | System OK | -- |
