Low Tyre Pressure Indicator Malfunction
Diagnostic Instructions
Circuit/System Description
The tire pressure monitor system has a radio frequency transmitting pressure sensor in each wheel/tire assembly. As vehicle speed increases, centrifugal force closes the sensors internal roll switch, which puts the sensor into Drive mode. The remote control door lock receiver receives and then sends the tyre pressure and temperature data to the body control module (BCM). The tyre pressure indicator module sends sensor ID and location data to the BCM. The BCM translates the data contained in the tire pressure sensor radio frequency transmissions into sensor presence, sensor mode, and tire pressure. Once vehicle speed is greater than 40 km/h (25 MPH), the remote control door lock receiver waits for the sensors to go into Drive mode.
Each sensor has its own unique identification (ID) code, which it transmits as part of each RF message, that must be learned into the BCM memory. Once all 4 IDs have been learned and vehicle speed is greater than 40 km/h (25 mph), the BCM continuously compares IDs and pressure data in the received transmissions to the learned IDs and pressures to determine if all 4 sensors are present and if one or more tyres are low. If the BCM detects a low tyre pressure condition, a variation in pressure between 2 tyres on the same axle, or a malfunction in the system, it will send a serial data message to the instrument cluster requesting the appropriate tyre pressure monitor indicator illumination and also to display the appropriate data message on the driver information centre, if equipped.
Diagnostic Aids
| • | If unsure about the condition, cycle the power switch and observe the tyre pressure monitor indicator icon. If the tire pressure monitor indicator icon is continuously illuminated after the instrument cluster 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, Tyre Placard, Anti-Theft, and Service Parts ID Label . If the tyre pressure monitor indicator icon flashes for 1 minute after the instrument cluster bulb check is completed and then remains illuminated, a tyre pressure monitor system DTC is set. Perform the Diagnostic System Check - Vehicle to proceed with the proper diagnosis. |
| • | Temperature can greatly affect tyre pressures. Low tyre pressure on a cold morning may cause the tyre pressure monitor indicator icon to turn ON. The air pressure in the tyre increases as the ambient temperature rises or as the tyre warms up while the vehicle is driven. The pressure may increase enough to exceed the predetermined low pressure threshold which will turn OFF the tyre pressure monitor indicator icon. |
| • | 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 BCM 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. |
Reference Information
Description and Operation
Tyre Pressure Monitor Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Note: Low tyre pressure in one or more tyres is indicated by a continuously illuminated tyre pressure monitor indicator icon after the instrument cluster bulb check is completed. If equipped with a driver information centre, a check tyre pressure type message will also be displayed.
When a tyre pressure monitor DTC is set, the tyre pressure monitor indicator icon will flash for 1 minute after the instrument cluster bulb check is completed and then remains illuminated. If equipped with a driver information center, a service tire monitor type message will also be displayed.
- Adjust all tyre pressures to the correct pressure. Refer to Vehicle Certification, Tyre Placard, Anti-Theft, and Service Parts ID Label
- Drive the vehicle over 40 km/h (25 mph) for greater than 9 minutes.
- Verify the low tyre pressure indicator is OFF.
| ⇒ | If the low tyre pressure indicator is ON
|
| 3.1. | Record each sensor tyre pressure parameter from the scan tool. |
| 3.2. | Check and record the tyre pressures with a known accurate hand held tyre pressure gauge. |
| 3.3. | Verify that the pressure readings from the scan tool do not differ more than 27.6 kPa (4 psi) from the actual tyre pressure readings. |
| ⇒ | If the pressure readings differ more than 27.6 kPa (4 psi), replace the appropriate B2 tyre pressure sensor then drive the vehicle over 40 km/h (25 mph) for more than 9 minutes. |
| ⇓ | If the pressure readings do not differ more than 27.6 kPa (4 psi) |
| ⇒ | If the BCM Tire Type and Pressure selections are incorrect, input the proper placard values for the vehicle with the scan tool then drive the vehicle over 40 km/h (25 mph) for more than 9 minutes. |
| ⇓ | If the BCM Tyre Type and Pressure selections are correct |
| 3.5. | Vehicle in Service Mode. |
| 3.6. | Verify the tyre pressure monitor indicator icon turns ON and OFF when commanding the instrument cluster All Indicators ON and OFF with a scan tool. |
| ⇒ | If the tyre pressure monitor icon does not turn ON and OFF, replace the P16 instrument cluster. |
| ⇓ | If the tyre pressure monitor icon turns ON and OFF |
| ⇓ | If the tyre pressure indicator is OFF
|
- All OK
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
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