My '93 just threw code #26, Quad-Driver Module #1 Circuit. Does anyone have an easy way to trace the exact problem. Where should I begin looking? From what I have read it could be any number of different problems that cause this code. Thanks for any ideas.

 

Omg I hope you have good luck with this. Just finally got done with my quad driver #3 nightmare.

 

Did you use any type of diagnostic scan tool, such as Tech 1. Was it helpful in diagnosing the problem or did you just have to check each element of each component?

 

A Tech 1 can be helpful to isolate the problem because it can actuate each solenoid and relay, if you hear it click when actuated it is working.

While not quite as easy you can diagnose the problem using the flow chart for code 26 in the Factory Service Manual, you will also need a Digital Volt Ohm Meter, or multimeter and a 12 volt test light. For those not familiar with using the book navigating through it can be intimidating, but don't let that discourage you.

The flow chart is located in book 2 on page 6E-A-56, find it first and place a page marker there, then do the same with the following pages:
8A-202-19 (pinout chart for the ECM) near the back of the book
6E3-C3-1 (Evap system description and component locations)
6E3-C6-1 (Secondary Air Injection system description and components)
6E3-7-1 (EGR system description and component location)

Knowing the appearance and location of the components will help as you follow the flow chart, but here are some tips that may help that are NOT in the FSM.

The solenoids are common failure items, the one for the EVAP system is under the passenger side fuel rail cover, the EGR solenoid is under the drivers side fuel rail cover, the Secondary Air Bypass solenoid is located near the ASR servo on the drivers side inner fender. After locating each one a quick and dirty test is to unplug them and test for resistance across the two pins with your DVOM. if there is no continuity at all (open or infinite reading) the solenoid is bad, replace it. If they all show some continuity, you will need to run the current test in the flow chart.

Another tip is to listen for your Secondary Air Pump when you first start the car, it is located near the left front headlight, it should run for a minute or two after start up then shut off, (it sounds like the cooling fan running) if it does that, you can probably rule it out as the problem and focus on the EGR or EVAP solenoids instead. Good luck.

 

Terrific info. Exactly what I needed, just a little guidance. Thanks alot. I'm going to jump into it.

Do you know what the scan tool costs, ballpark?

 

Shoot me a PM if you get into the diagnosis and need some assistance, I'll try to help.
Try to find a Tech 1 or Tech 1A that has the Mass Storage Cartridge, P/N 30000003 that one should have all the software you will need, expect to pay around $400 for it so equipped, more if it has a lot of other accessories.
Unless you plan to use the tool on other vehicles, the basic tool with MSC should handle most of what you need on your 93, one nice extra would be the SIR Dual UARTcable adapter, you may need that for air bag diagnosis.

 

Having been down this road, the way to check if the EGR solenoid is the problem. Clear the codes, then get on a long straight highway and drive at 75-80 mph, this should make the ECM activate the EGR and trigger your engine light.
If your light comes on in city traffic, 10 bucks says it is your Evap canister purge solenoid, located right next to the #2 injector.
It has 2 hoses, you can't miss it and listen to Toptechx6, he helped me out a great deal diagnosing my problems.

 

yep, Jim's a very smart cookie!

 

Thanks again. I'll let you know how I make out.

 

I just had this code 26 recently. If the code is the same for the 93 as the 94 it was then the Evaporative Emission Canister Purge Solenoid Valve. Bottom line is I ended up replacing it and I was fixed. You can read about my details in this post. Hope this helps in regard to your problem.

http://forums.corvetteforum.com/c4-t...e-circuit.html