A 2017 Silverado LTZ 6.2 presented with a Check Engine Light (CEL) and no noticeable performance issues. A diagnostic scan revealed two Diagnostic Trouble Codes (DTCs): U1501 and U1510 in the Powertrain Control Module (PCM), both indicating a communication problem on the Local Interconnect Network (LIN) bus. This article outlines the diagnostic process used to pinpoint and resolve the issue.
Initial Assessment and Research
Research on the U1510 code pointed to a potential ground (G102) failure, often associated with intermittent right front headlight issues. However, the customer reported no lighting problems. Despite this, G102 was inspected and tested. Although appearing corroded, the ground measured approximately 50mV under load with high beams activated, indicating no significant issue.
Narrowing Down the Culprit
Consulting the vehicle’s wiring diagram revealed the Active Grille Shutter Motor Module as the sole module communicating with the PCM on the affected LIN bus. This significantly narrowed the scope of the diagnosis.
LIN Bus Waveform Analysis
Accessing connector X132, located behind the front grille, allowed for direct examination of the LIN bus communication wire (GREEN/VIOLET). Connecting an oscilloscope revealed a seemingly normal waveform. However, closer inspection showed the bus voltage only being pulled down to 7 volts, instead of the expected battery voltage (around 12 volts). This deviation suggested a potential problem with the Active Grille Shutter Module, its power supply, ground connection, or the wiring between X132 and the module’s connector.
Disconnecting X132 and re-examining the waveform confirmed the suspicion. The bus voltage now correctly pulled down to battery voltage, isolating the fault to the Active Grille Shutter Module circuit.
Verification and Repair
Load testing the power and ground circuits of the Active Grille Shutter Module revealed no deficiencies. Based on the waveform analysis and the subsequent tests, a new Active Grille Shutter Module was installed. This resolved the communication issue and extinguished the CEL, confirming the faulty module as the root cause of the U1501 and U1510 DTCs.
Conclusion
Systematic diagnosis, utilizing wiring diagrams and oscilloscope waveform analysis, proved crucial in identifying the faulty Active Grille Shutter Module as the source of the U1501 and U1510 codes in this 2017 Silverado. This case highlights the importance of understanding communication protocols like LIN and leveraging diagnostic tools for effective troubleshooting.
