'94 Cavalier Error Code?

static1701January 15, 2006

My '94 Cavalier is setting the following codes:

DTC27 QDMB Fault

(When this sets, the cooling fan comes on and stays on) I have tested both relays with the gm tech 1. I have not been able to find what the code means.

While I was at it, I fould codes for my ABS system, the first two I think are because I removed the dash warning lamp years ago. Since I was able to test it now, I would like to find out what the codes mean. The ABS codes are:

11 lamp open

46h rear channel

87 ???

The ABS has not worked for years, no big deal but I would like to fix the fan problem.



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malfunctioning cooling fan temperature sensor
ABS sensor, rear, broken or bad connection or dirty
Check out one, or both,of the OBD forums

    Bookmark   January 15, 2006 at 5:54PM
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I replaced the temp sensor, still has the same problem.
Until I can figure this out, I have disconnected the cooling fan. The car never warms up with it running all the time.


    Bookmark   January 16, 2006 at 10:52PM
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Its not advisable to disconnect the cooling fan!

Try this. After you have replaced the temperature sensor (and reconnected the fan), erase the trouble code to see if this puts you back to normal operation.

    Bookmark   January 17, 2006 at 2:20AM
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I looked up the codes at work today, I found that the code 27 is Quad-driver module and it points to EGR purge solenoid or evap canister solenoid. Nothing to do with the temp sensor at all. I did try clearing the code, but it re-sets. The flow chart I have now says to cycle the purge solenoid (Make sure it works) I know that disconnecting the fan is not a good idea, but since I am in MI and it is all of 27 degrees today I don't think it is going to overheat. The problem is I don't have access to the tech1 scanner all the time, it belongs to a co-worker of a friend. I do have access to a tech2, but I can't find the correct cable adapter to use it. Based on the flow chart from alldata, I am going to check the purge solenoid and go from there.


    Bookmark   January 17, 2006 at 8:41AM
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Make sure you are chasing the right thing. If you can get the Tech I or II hooked up again see if you can see what is calling for the fan to turn. Like what temp. does the ECM see? Does the ECM see the AC on? Also look at the link below.


Good Luck

    Bookmark   January 17, 2006 at 11:01AM
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The relay is an electric switch;usually, maybe 99.99% of the time - for all I know - they malfunction in an open or off position..
But if the fan relay stays in the closed or on position, then this would explain why the fan stays on..
Switching relays is one method of checking this out..

And there are many reasons for this problem.
The electrical schematic is necessary..

    Bookmark   January 17, 2006 at 11:20AM
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The reason I think it is the egr purge solenoid is from what the alldata sites says for DTC27 QDMB fault

DTC 27 will set when QDMB Fault line:
Is "High" for 20 seconds or more
tcc is commanded "On" (My car is a stick, so this does not apply)
Battery voltage is greater then 10.5 volts

Action taken: The Malfunction Lamp (MIL) will illuminate, and the cooling fan will enable.

DTC test description:

Check to see if DTC27 was set as a result of the EVAP canister purge solenoid valve circuit

Check tcc operation

Check intergrity of EGR circuit up to the solenoid.

So from what I can see, it looks like the purge solenoid becuase when I had the tech 1, I did test the EGR solenoid (I had an old stored EGR code) I also tested both the A/C fan relay and the engine fan relay and I was able to start stop the fan from the tech 1. I did not test the purge solenoid because at the time, I did not know what DTC27 ment.

Provided the freezing rain stops when I get home, I am going to swap cars around and pull it into the garage and check that purge solenoid.

The thing that I can't understand, is why did GM have the cooling fan come on for an EGR system fault?


    Bookmark   January 17, 2006 at 12:02PM
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I changed out the purge solenoid and it fixed that problem, now it sets code 32. I have to check the lines to the EGR valve, alldata points to a plugged line. Sure is a pain for something I wish the car did not even have.

    Bookmark   January 25, 2006 at 10:22PM
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