Diagnostic Instructions
Circuit/System Description
The lift gate module (LGM) receives a radio frequency (RF) transmission from each tire pressure sensor. Each sensor has its own unique identification (ID) code, which it transmits as part of each RF message, that must be learned into the LGM memory. Once
all 4 IDs have been learned and vehicle speed is greater than 40 km/h (25 mph), the LGM continuously compares IDs in received transmission to its learned IDs to determine if all 4 sensors are present. If the LGM detects a low
tire pressure condition or a malfunction in the system, it will send a serial data message to the instrument panel cluster (IPC) requesting the appropriate tire pressure monitor indicator illumination and also to display the appropriate data message on the driver
information center (DIC), if equipped.
Diagnostic Aids
| • | If unsure about the condition, cycle the ignition and observe the tire pressure monitor indicator icon. If the tire pressure monitor indicator icon is continuously illuminated after the IPC bulb check is completed, a low tire pressure condition is
present. Check the tires for damage or leaks and inflate to the tire placard specifications. Refer to
Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label. If the tire pressure monitor indicator
icon flashes for 1 minute after the IPC bulb check is completed and then remains illuminated, a tire pressure monitor system DTC is set. Perform the
Diagnostic System Check - Vehicle to proceed with the proper
diagnosis. |
| • | Temperature can greatly effect tire pressures. Low tire pressure on a cold morning may cause the tire pressure monitor indicator icon to turn ON. The air pressure in the tire increases as the ambient temperature rises or as the tire warms up while
the vehicle is driven. The pressure may increase enough to exceed the predetermined low pressure threshold which will turn OFF the tire pressure monitor indicator icon. |
| • | Some aftermarket wheel valve stem holes are located further from the wheel rim than original equipment wheels. When using the TPM special tool to activate a sensor, ensure the tool antenna is no further than 15 cm (6 in) from
the sensor and is aiming upward. |
| • | Aftermarket wheel value stem locations can cause a sensor to not function correctly. |
| • | A sensor may have been damaged due to a previous wheel/tire service or flat tire event. |
| • | The use of other than GM approved tire sealants can obstruct the sensor pressure sensing port and cause inaccurate tire pressure readings. If this condition is verified, remove the sealer from the tire and replace the sensor. Refer to
Tire Pressure Indicator Sensor Replacement. |
| • | Occasionally sensor transmissions are not received by the LGM due to vehicle level RF interference from items such as but not limited to aftermarket ignition systems, DVD players, CB radios, or metallic type window tinting. |
| • | The sensor activation procedure may have to be repeated up to 3 times before determining a sensor is malfunctioning. In the event a particular sensor's information is displayed on the special tool upon activation but the horn does not chirp,
it may be necessary to rotate the wheel valve stem to a different position due to the RF signal is being blocked by another component. |
| • | Occasionally sensors can become mislocated due to previous tire rotations where the sensor learn procedure was not performed or stray sensor transmissions have been received from other vehicles. Always learn the sensors to ensure the DTC set is for
that actual physical corner of the vehicle. Refer to
Tire Pressure Sensor Learn. |
Reference Information
Description and Operation
Tire Pressure Monitor Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
J-46079
Tire Pressure Monitor Diagnostic Tool
Circuit/System Verification
Note: Low tire pressure in one or more tires is indicated by a continuously illuminated tire pressure monitor indicator icon after the IPC bulb check is completed. If equipped with a DIC, a check tire pressure type message will also
be displayed. It is not necessary to perform the Learn procedure for a low tire condition.
When a TPM DTC is set, the tire pressure monitor indicator icon will flash for 1 minute after the IPC bulb check is completed and then remains illuminated.
If equipped with a DIC, a service tire monitor type message will also be displayed.
- Verify all tires are inflated to the proper pressure ±10%. Refer to
Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label.
| ⇒ | If not within the specified range, adjust all tire pressures to specification and drive the vehicle over 40 km/h (25 mph) for greater than 2 minutes. Verify the tire pressure monitor indicator icon is OFF. |
- Using the
J-46079
, activate each tire pressure sensor and record each sensor tire pressure reading. Check the tire pressures with a known accurate hand held tire pressure gauge. Verify that
the pressure readings from the special tool do not differ more than 27.6 kPa (4 psi) from the actual tire pressure readings.
| ⇒ | If not within the specified range, replace the appropriate tire pressure sensor. |
- Using a scan tool, enable the TPM learn mode. Use the
J-46079
in simulate mode to learn 4 simulated sensor transmissions into the LGM. Observe tire pressures in the scan tool data display.
Verify the simulated tire pressures do not differ more than +/-27.6 kPa (4 psi) of the scan tool reading.
| ⇒ | If not within the specified range, replace the LGM. |
- Using a scan tool, perform the instrument panel special functions Lamp Test. Command the instrument panel warning lamps ON and OFF. Verify the tire pressure monitor indicator icon turns ON and OFF.
| ⇒ | If the tire pressure monitor icon does not turn ON and OFF, replace the IPC. |
- Ignition ON, use the scan tool to setup the Tire Type/Pressure Selection in the LGM Module Setup menu. Refer to the
Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label. Drive the
vehicle over 40 km/h (25 mph) for greater than 2 minutes. Verify the tire pressure monitor indicator icon is OFF.
| ⇒ | If the tire pressure monitor icon does not turn OFF, replace the LGM. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
