Too many vehicles in the shop? Don’t have time to perform a thorough diagnosis on each one? Use this Real Fix to thin the herd by diagnosing your customer’s vehicle that has a similar symptom.

Vehicle

2003 Chevrolet Tahoe, 5.3L

Complaint

The customer states the vehicle’s tachometer does not respond to the change in engine speed.

Cause

Performed a road test to duplicate the customer’s concern and found the vehicle’s tachometer did not respond to the change in engine speed. Performed a road test while monitoring live data on the scan tool and observed the tachometer readings differed from the engine speed data parameter readings. Connected a lab scope to the RPM OUT terminal at powertrain control module connector 2, measured the voltage signal and observed the signal did not change when the engine speed varied. Disassembled the engine wiring harness, traced the RPM OUT circuit and discovered the RPM OUT wire had stretched in the engine wiring harness, which caused the open circuit.

Correction

Repaired the engine wiring harness, cleared codes, performed a road test and verified the vehicle operated properly.

Courtesy of Mitchell 1 SureTrack Real Fix