jwbeaumont

I'm sure I'm not the only one out there with this problem.

I have a 1993 Z28 with 89,000 miles on it. It has zero mods.

After the car runs for a few minutes, the SES light comes on. My code reader gives me the #26, which says it is the EVAP purge solenoid. I put a new one on, and the light still comes on.

Now, the light doesn't come on until the engine warms a little and I can hear the fan kick on. So far, the mileage has not changed and the car does not run hot or anything. Everything seems normal, except the fan kicking on, then the light immediately after the fan.

What else could this be? Anyone else have this same problem? What fixed it?

Guest47904

On a 94 the same fuse is used for the fans and the EVAP solenoid. If 93 is the same, then there is no need to check the fuse since the fans are running. However if in 93 there was a different fuse for the evap solenoid then the fans, it could be worth looking for.

The evap solenoid is turned on by grounding one side of the solenoid coil by the PCM. The other side of the evap coil is connected to 12 volts through a fuse (usually #6 underhood) to the ignition. The PCM monitors the wire from the solenoid that is connected to the PCM to see that it has 12 volts up to the time the PCM grounds the wire to turn on the solenoid. Chances are that a wire or connector is either broke, not making contact or otherwise interrupting continuity.

The place to start is the PCM connector off the PCM with the key on. Measure the voltage on the wire connected to the evap solenoid to see that it has 12 volts when measured to ground.

On a 94 the wire that goes from the solenoid to the PCM is dark green with a white stripe and it goes to the blue PCM connector pin 10. Again I emphasize that a 93 is it's own unique beast and the wiring may be different. Take a look at the wire color on the solenoid and the blue PCM connector. If they are different, find a 93 manual complete with wire colors like the GM shop manual or perhaps shout out for a wire color on one of the other message boards.

Injuneer

Since you have a 93, you have to use the 93 code list. If you look at the far right hand column on Shoebox's LT1/OBD-I code list, you will find these three items listed for a 93, because they are all driven off the same "quad driver" module (only used up to 1993):

Quad-Driver Module (QDM) #1 circuit
applies to:
- AIR pump relay circuit
- EGR solenoid
- EVAP solenoid

http://shbox.com/1/Dtcs.htm

You need to check all three of those, and if they are all OK, it may be a failure of the quad driver module. Check the AIR pump fuse first.

blac94Z

hey had to awake the dead, so i finally scanned my car and i see i have this code on but i just changed this in dec along with all hoses and canister what could be my problem ?

Injuneer

Since you have DTC 26 and a 1994, you have a problem on the electrical circuit for the EVAP purge solenoid. The solenoid needs to be checked for continuity. I think it runs about 30 ohms resistance. Then check the harness connector, off the solenoid. Key on, engine off, measure the voltage between the brown wire and a good engine ground. Should be 12V. The PCM supplies the ground to open the solenoid on the dk green/white wire. You could test the continuity of that wire from the harness connector pin to pin D10 on the PCM. Alternatively, I think GaryDoug's Scan9495 has the capability to command the ground to the solenoid..... have to verify that.

blac94Z

i will have to test it when i get home can this mess up my new valve i just put on ?

Injuneer

Testing the circuit shouldn't hurt the solenoid. But the solenoid needs to be checked to make sure it's not causing the code.

GaryDoug

Yes it does. It can be forced to on or off. As a result, the variable value in the table will show either 0% (off) or 100% (on).
Shouldn't hurt anything.

Fatdog2

My code reader book for 1982-1995 cars and trucks says code # 26 is Quad-Driver module or Quad driver No.2 error.(From the glossary in the same book definition =Quad-Driver(QDM)Computer chip,in the PCM,capable of operating four separate outputs.Some have digital and some have pulse width modulated outputs).Hope this helps cause I haven't a clue what all this means.My brain would explode.My 02.

GaryDoug

That would be correct for 93, but not 94 or 95. DTC26 for a 94 is as Fred explained.

And by the way, DTC26 on a 93 is for QDM#1.

Injuneer

There is no substitute for Shoebox's LT1 SPECIFIC code list, showing the differences between the 93's and all other years:

http://shbox.com/1/Dtcs.htm

The "generic" published lists, and the explanations that show up on some scanners are not reliable.

Injuneer

The "topic" does not describe the vehicle blac94Z is asking about. He has a 94, and tacked his post onto an old thread.

There is no substitute for Shoebox's LT1 SPECIFIC code list, showing the differences between the 93's and all other years:

http://shbox.com/1/Dtcs.htm

The "generic" published lists, and the explanations that show up on some scanners are not reliable.

blac94Z

when i asked if it will mess the valve up i ment will it make my canister overflow again ?