What's wrong

  • 1993 SATURN SL2
Car will die while driving but will restart after 20min but die again after driving 4mil. Trouble code 26 Quad driver output fault I've replaced coil packs and ignition module but now think it's fuel problem. Strong fuel oder
Do you
have the same problem?
Tuesday, February 7th, 2012 AT 7:41 PM

2 Replies

The "Quad Driver" is a device in the computer that "drives" electro-
mechanical devices in the car. Computers run with very little current
(milliamps or microamps) in their circuits. But the devices that
turn on your cooling fan, bulbs, or emissions relays may require
current in a higher range, say tenths of an amp.

Thus, the computer can't talk very well with such a high current
device. It needs help, and it gets in in the form of this Quad Driver
device. The computer sends a signal (very low amps) to the driver, and
it in turn then signals the electromechanical device to do whatever it
needs to do with a higher current which that device can use.

It sort of "drives" the device by remote control.

Code 26

OK, fine, that is the theory. So why the code 26? Well, in almost all
cases, the actual driver device does not fail. What fails is one of
the electro-mechanical devices attached to it. The way the SES light
works, it will come on when either one of the driven devices fails or
if the driver itself fails.

The good news is it is usually not the costly driver device. The bad
news is this is called a "QUAD" driver. That means it drives four
devices. Even worse, there are usually TWO quad drivers, so you have
a total of EIGHT devices to check for just this one SES light.

That's right, code 26 means that one of 8 devices (and a 9th, the driver
itself), could cause the problem. You have to check 8 different things.

Probable causes

I don't have my manual here, but I'll try to remember to post the
exact devices to check. The following is from memory, so bear with me.
Also, remember my car is a '91, so this may have changed somewhat in
following years.

The QD generally drives things like relays, solenoids and light bulbs.
There are a few things that are easy to check, like the bulbs and

The SES bulb and (I think) "HOT" bulb are driven by this device. You
should check that they both come on when you put the car to "on" before
starting. Of course, the SES must work, since it came on for you.

Then the A/C relay and Cooling fan relay are driven. For A/C, simply
check that your A/C works OK. The relay is pretty silent, unlike
some cars, so you can't always hear it click. Just make sure it works.
The cooling fan can be checked when you sucked out the code. Since you
know how to get the code, you should have noticed that the FAN comes
on for a while before getting the code out. (The bulbs also light.)
If the fan isn't coming on, check the relay. The Haynes manual probably
tells you exactly when the fan comes on during the procedure.
The relay is accessible in the under-hood fuse block.

After that, it gets tougher. You have to check some emissions solenoids.
From what I've read, the MOST COMMON cause of code 26 is either the
EGR solenoid or the canister purge solenoid. The EGR solenoid is
real easy to access. It sits right above the EGR valve and takes a minute
to disconnect on Sx2 models. The canister purge solenoid is a pain.
It is attached to the block on the firewall side. You have to take it
out blindly by putting your hand through a small "hole" between all the
hoses and wires.

I forgot what else is controlled by this device. I'll try to get
my manual tonight to look.

I had an SES light last spring. In my case, I guessed wrong.

I narrowed my SES last year down to the CPS or the EGRS, and incorrectly
deduced the CPS. What a pain to replace this. But I was wrong. That
wasted $20. My problem was the EGRS, and it was also a $20 part. Very
easy to replace.

I should mention that my symptoms were opposite of yours. Mine would
come on only while driving for a while, then go off when I stopped.
I should also mention that the CPS and EGRS are common causes of
code 26, and the irony is they are both Nippondenso parts, made in
Japan. How ironic!

Either way, if you take it for service, the Saturn diagnostic computer
should be able to discern between the two or any other device that
is causing this code. They can read more information than we can
by just pulsing out codes.

So, depending on your skill and your luck, you may or may not want to
try this. Like I said, most of the them are easy, thus even if Saturn
service does it, it usually is not costly.
Was this
Tuesday, February 7th, 2012 AT 7:47 PM
If you keep starting a new question like you are and dont stick to the same one how is anyone supposed to help you?Iam trying my best to help you but all you do is keep starting new questions. If your looking for a magic answer its just not there for your concern your going to have to test somethings.I have worked for saturn for over 16yrs I know these cars well. When it dies and wont start check for spark if you have spark then check for fuel pressure. Also like I said before those cars have a known problem with there coolant temp sensors. Please stick to this question for your replies and stop starting new questions. Doing that is really getting you no where all you have to do is click the link in your email alert and it will take you back to this question.
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Tuesday, February 7th, 2012 AT 7:49 PM

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