E026

[NCReatta]

I'm getting an E026 code on my '89. Manual says its a QDM fault..

What is this and how do I fix it? It can't be too bad as it only comes on occasionally, and the car drives great.

Any thoughts are appreciated! Thanks!

[padgett]

That is the infamous "Quad Driver" and you have to test a bunch of things to figure out which - is the TCC working properly ?

[NCReatta]

That is the infamous "Quad Driver" and you have to test a bunch of things to figure out which - is the TCC working properly ?

Yeah, well sorta a guess.. I can get it into passing gear, but it used to go into one gear above passing gear. I don't think it's been doing that since the code was tripped.

[Guest Mc_Reatta]

Using the on-board diagnostics makes it fairly simple to track down which circuit is tripping the E026 code.

Read the section on the E026 code starting on page 8D1-36 in the 89 FSM. Tells you how to check the canister purge and TCC solenoids and EGR, AC and fan relays, which can trip the code along with the SES and HOT warning lights.

[KDirk]

FYI, the QDM is just an integrated circuit used as an interface to control outboard devices. The IC is on the circuit board within the ECM, and could probably be replaced if the equivalent part number could be sourced. Once again, GM/Delco's house numbering system for IC's and transistors is the bane of our existence.

KDirk