ASE A4 Suspension and SteeringWheels and Tires Diagnosis and RepairHard
A technician is diagnosing a tire pressure monitoring system (TPMS) issue. The TPMS warning light is on, and a scan tool shows Diagnostic Trouble Code (DTC) C0040, indicating a 'Left Front Tire Pressure Sensor Malfunction.' After replacing the left front sensor, the technician attempts to perform a relearn procedure. The relearn process fails repeatedly. Which of the following is the MOST likely reason for the relearn failure?
- AThe vehicle speed was too high during the relearn attempt.
- BThe new sensor requires a specific programming tool before relearn.
- CThe tire pressure in the other three tires is incorrect.
- DThe vehicle's battery voltage is too low during the relearn procedure.
Show answer & explanationAnswer & explanation
Correct answer: D. The vehicle's battery voltage is too low during the relearn procedure.
Many TPMS relearn procedures require stable system voltage. Low battery voltage can disrupt the communication signals or the vehicle's ability to complete the sequence, leading to relearn failure.
Why the other options are wrong
- A. Relearn procedures are generally performed stationary or at very low speeds, or a specific driving cycle is required, but 'too high' speed would only apply if the procedure involved driving, and failure to meet speed requirements would be a specific step failure, not a general system communication failure often caused by low voltage.
- B. While some universal sensors require programming, OEM or pre-programmed aftermarket sensors typically do not require an additional programming tool before a relearn, only after replacement. The question implies the sensor was replaced, not that it's a universal sensor needing initial programming.
- C. Incorrect tire pressure in other tires would trigger TPMS warnings but typically would not prevent the relearn procedure itself from completing, as the relearn focuses on identifying the sensors.
TPMS Relearn Failure Causes
Reasons why a Tire Pressure Monitoring System (TPMS) might fail to successfully register new or replaced sensors.
- Low battery voltage can disrupt communication.
- Incorrect relearn procedure steps or sequence.
- Interference from other electronic devices.
- Faulty new sensor or TPMS control module.
Memory trick: Low volts make TPMS 'relearn' its lesson the hard way.