SureTrack Real Fix: Fix of the Century

Real Fixes from ShopKey’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available free with the purchase of a current Snap-on® diagnostic software version or in our ShopKey Pro product.


Ok, well maybe not the fix OF the century but a fix for a Buick Century. Follow this Real Fix to see how a code 26 for the Quad Driver Circuit was diagnosed and repaired on this 1990 Century.

Vehicle
1990 Buick Century Custom 3.3L

Title
Code 26, Replaced Powertrain Control Module

Complaint
The customer states the check engine light is on.

Cause
Connected a scan tool and found code 26 – Quad Driver Circuit. With the key on, engine off, connected a fused jumper between the diagnostic link connector terminals A and B, observed the evaporative emission (EVAP) purge solenoid, the low speed engine cooling fan relay and the torque converter clutch solenoid, and found there was no audible click heard from the EVAP purge solenoid. Connected a test light across the EVAP purge solenoid connector terminals and found the test light illuminated. Disconnected the fused jumper from the diagnostic link connector and found the test light was still illuminated. The test light should have been off. Disconnected the powertrain control module and found the test light was no longer illuminated. These test results verified the powertrain control module was faulty.

Correction
Replaced the powertrain control module, cleared codes, performed a road test and verified the vehicle operated properly.


SureTrack® adds to the power of ShopKey Pro with an exclusive combination of expert knowledge and detailed parts replacement records, all wrapped in an interactive community. Designed to help automotive shops increase accuracy and efficiency from diagnosis to completed repair, the industry’s most comprehensive repair information resource is just a few clicks away.

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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.