The Technical Services team at Airtex Vehicle Electronics has released a fascinating diagnostic video that unlocks the secret to intermittent P0171 trouble codes on some Chevrolet Trailblazer models.
The new seven-and-a-half-minute video, “P0171 Chevrolet Trailblazer Diagnostics,” explores the reasons for intermittent lean fuel conditions – and the resulting diagnostic trouble code – on a 2006 Trailblazer equipped with a 4.2-liter engine. “Inspector Tech,” a new figure in the Airtex Vehicle Electronics series, accepts the case after a vehicle dealership is unable to eliminate the issue by replacing O2 sensors and intake manifold gaskets.
“As Inspector Tech reminds the viewer, it’s always a mistake to start replacing parts before you have collected all of the evidence,” explains Jim Gehl, technical services instructor for Airtex Vehicle Electronics. “In this case, both the dealership and an independent shop should have studied a number of parameters in the freeze frames and recorded movies available through their scan tools.”
The Airtex team discovered that the vehicle consistently experienced a spike in long-term fuel trim after approximately eight minutes of operation following a cold start, indicating that excess oxygen was entering the exhaust system upstream of the front 02 sensor. Through additional research into the vehicle’s emissions control equipment, the team determined that the probable cause was a malfunctioning air solenoid control valve in the vehicle’s secondary air injection system. This system helps reduce catalyst light-off time by introducing pressurized fresh air into the exhaust stream during cold warm-up. A comparatively inexpensive new air solenoid control valve solved the problem.
“This is great example of the value of performing a truly comprehensive diagnosis using modern equipment,” Gehl said. “Two service providers had spent hours trying to solve the problem without having all of the necessary data. More importantly, they had lost the confidence of the vehicle owner.”
The new program is the latest in a series of nearly 25 hands-on diagnostic case study videos available through the “Tech Tools” link at www.airtexVE.com. These videos also are available through the Airtex Vehicle Electronics channel at www.YouTube.com.
For more information regarding Airtex Vehicle Electronics diagnostic resources and the company’s comprehensive range of premium quality replacement vehicle electronics, visit www.airtexVE.com.
