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Thread: Possible ECM/PCM problem 93 TBI 350

  1. #11
    Senior Member dk-93silverado's Avatar
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    I am guilty as charged. I have a Powertrain Control Module because my transmission is electronically controlled by the same module that controls my fuel injection. I didn't really swap the engine wiring harness. The wiring harness I am using was from a 94 and was VASTLY different. I completely stripped it down to wire and recreated each circuit one at a time. The PCM connectors were completely different for starters. Many circuits were similar or even the same and many were completely different or non existent. I have hours of testing in this harness to verify each circuit but I am not afraid to go over it again and again if necessary. My ICM is brand new and has been tested but I would never assume a new electrical component is functional until I have tested it myself.
    Through some research I found out that in 91-92 They used QDRII which temporarily shut down and then reset if a device or its circuit shorts. Unlike QDR which are permanently damaged if a device or its circuit shorts because of no added circuit protection. I was not sure if my PCM had QDRII but you have informed me. Here is an explanation I want to post in case someone else reads this in the future. It could be vital for proper diagnosis and or understanding of these drivers.

    Looking at the ECM and its quad drivers. Most ECM controlled devices are either solenoids or relays. Typically, solenoids are used for a circuit when the current draw is 0.75 amps or less, and relays are used in a circuit when the normal current draw is expected to exceed 0.75 amps. GM uses quad driver circuits inside the ECM to control the outputs to these devices. So quad drivers (QD) are integrated circuits inside the ECM that it uses to close or open the circuit path to ground, turning the device on or off. Depending on the make and model year GM vehicles use different variations of quad drivers.
    Now lets look at testing quad driver devices and their circuits.
    As we've all ready seen, most quad driver circuit faults are due to a short in a device or its circuit. (Wiring/connectors). However at times a device or circuit that is open will set a quad driver fault code.
    Before replacing an ECM, always isolate the problem device or circuit. Replace the defective device or repair the circuit, and resets.
    Each quad driver can control up to four devices. So diagrams will have to be used to find which devices the quad driver at fault is controlling.
    Below is a typical diagram of QDM circuits. If this diagram was for quad driver B and that was the code that was set, we now know that this QDM controls, the TCC sol. Purge control sol. EGR control sol, and the check engine lamp.
    A real diagram would list all circuit numbers, the wire colors, and connector terminal numbers. The important thing is that each device and circuit is tested, found to be good or repaired as necessary. The proper test on these circuits would be, with key off disconnect all ECM connectors, then with an amp meter set on the 10 amp scale connected to the control side of the circuit at the ECM connector and to ground turn the key on and check that the device turns on. With the device turned on, the meter should read 0.75 amps or less. Run this test for at least five minutes to make sure the device isn't overheating and shorting. The TCC solenoid cannot be tested in this manner in a vehicle that has a normally open third gear switch inside the transmission. A scanner thrtough an extended road test best checks the TCC circuit.


    A normally operating device and its circuit will have at least 20 ohms of resistance and can be checked with an ohmmeter. This will tell if the circuit or device is open however, this will not place the device in operation. So if the device is only failing due to heat after being in use for a period of time the fault will not be found with a resistance test.
    With the proper test equipment it's fairly easy to determine what circuit or device is causing a quad driver fault.
    You will need a good digital multimeter and, if this first time buy the best would be one that has a 20 amp fused capability. The larger amp rating can come in handy when testing other electrical systems of your vehicle.
    Also two 10 amp fused jumper wires keeping the in-line fuse as close to the power supply circuit as possible.

    ęCopyright 2001-2007 batauto.com, BAT Auto Technical.
    All Rights Reserved. I found this information at Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical
    http://www.batauto.com/articles/quaddriver.shtml
    Last edited by crabtruck; 12-17-2010 at 10:29 AM. Reason: fix link to article

  2. #12
    Senior Member dk-93silverado's Avatar
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    I failed to mention that I did pull three codes yesterday.
    59-Trans temp low
    81-Trans 2-3 error
    82-Trans 1-2 error
    This tells me that I still need to work on that part of the wiring harness. I will be rendering that soon. I have a strong feeling that it is just a mistake on my end.

  3. #13
    Senior Member dk-93silverado's Avatar
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    "If you have the wire from F11 to Ign control mod(D=Wht) grounded/short, then no start.
    If you have the light connector for injectors, you can test Ign mod though
    PCM to Inj process with a test light. Unplug 4-wire on ICmod, turn key on.
    Connect a test light to battery and tap the IC Ref-Hi wire in plug (C=Ppl/Wht).
    Each time "tap" is removed, injector light should flash. Yes means Ign mod problem.
    No flash from Inj after tap says connections back to PCM or PCM bad."


    IC is D11 on my 93 PCM. For some reason the 94 had A,B,E and F PCM connectors. My 93 has A,B,C and D. This made things interesting when swapping pins to 93 connectors. I would have been dead in the water if it weren't for the All Data PCM pin outs. Any way I preformed said test by tapping IC reference-high and injectors were actuated. I knew For a fact that my white IC wire had continuity to PCM via back probing PCM pin. This test double verifies that connection and verifies the valuable function of quad driver. I did test my new ICM at oreillys but I am currently looking into this again. Thank you for referring me to this test procedure.

  4. #14
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    You've near proved failed output of IC, however, while you said white good to PCM,
    I am not seeing that you confirmed no short to ground. Did I miss that ?

    Codes 81 & 82 could just be blown 10A Trans fuse.

    In 94 the ECM (5.0 w/MT & 5.7 w/MT) uses a 24pin A/B and a 32pin C/D.
    The PCM (all other incl. 4.3 w/MT &7.4 w/MT) uses a red 32pin A/B and blue 32pin E/F.
    I had thought 93 followed same pattern. Was this originally MT ?
    Can you post a pinout for what you're using ? Are orig connectors black (before fire) ?

    Some good info in quoted item, but I doubt certain portions of it.
    Discussion for another time. Where did you find it ?

  5. #15
    Senior Member dk-93silverado's Avatar
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    Quote Originally Posted by crabtruck View Post
    You've near proved failed output of IC, however, while you said white good to PCM,
    I am not seeing that you confirmed no short to ground. Did I miss that ?

    Codes 81 & 82 could just be blown 10A Trans fuse.

    In 94 the ECM (5.0 w/MT & 5.7 w/MT) uses a 24pin A/B and a 32pin C/D.
    The PCM (all other incl. 4.3 w/MT &7.4 w/MT) uses a red 32pin A/B and blue 32pin E/F.
    I had thought 93 followed same pattern. Was this originally MT ?
    Can you post a pinout for what you're using ? Are orig connectors black (before fire) ?

    Some good info in quoted item, but I doubt certain portions of it.
    Discussion for another time. Where did you find it ?

    No I did not post results from ground test at IC signal to PCM. The white wire has no continuity to ground when PCM connector is unplugged and ICM unplugged (just testing isolated wire end to end).With PCM connector Installed and ICM still unplugged the white wire has continuity to ground.

    I wish code 81 and 82 were a blown fuse but not the case.

    I have a pinout for a 94 k2500 350 w/ 4l80e and a pinout for a 93 k2500 350 w/4l80e. Both of my pinouts are on paper only but I can scan those dirty bastards.
    The 94 has two 32 pin connectors a,b,e and f. One was blue and the other red. My 93 harness used two brown connectors. a,b is a 24 pin and c,d is a 32 pin. I am actually using the original brown PCM connectors from the factory harness. It was a factory 4l80e package. I just pulled all the pins. I have a spare engine wiring harness that has the older style TPS. It has black connectors and was from a truck using a 350 and 700R4. That one dosn't have anything to do with this operation.

    I found the info on Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical











  6. #16
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    If I followed that right, you are connecting to/currently using a 24pin A/B.
    For 94 that was for MT w/ ECM not PCM. Was that not so in 93 ?

  7. #17
    Senior Member dk-93silverado's Avatar
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    This is the exact page I got the info from. Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

    I have some pictures of the harness modification in my photo gallery. I'll see about scanning my pinouts. They are interesting with all my marks and labels from much use.

  8. #18
    Senior Member dk-93silverado's Avatar
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    Quote Originally Posted by crabtruck View Post
    If I followed that right, you are connecting to/currently using a 24pin A/B.
    For 94 that was for MT w/ ECM not PCM. Was that not so in 93 ?
    In 93 for 4l80e application, PCM used 24pin A/B. This is what I am using. Is that what you were looking for? For the record I verified by VIN that this truck came with 4l80e. That could be irrelevant.
    Last edited by dk-93silverado; 11-12-2009 at 06:31 PM. Reason: added information.

  9. #19
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    Yes that's what I was saying: 94 used 24pin/ECM for MT's only.
    93, you are saying, used 24pin/PCM for AT's. Pinout will be interesting.

    Another thought: does this list as HD for engine ? Using linear EGR etc.
    They used to call the 4L80E's the HD trans.
    About 4 kinds of "HD" possible on same truck,
    GM keeping things simple and all.

  10. #20
    Senior Member dk-93silverado's Avatar
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    Quote Originally Posted by crabtruck View Post
    Yes that's what I was saying: 94 used 24pin/ECM for MT's only.
    93, you are saying, used 24pin/PCM for AT's. Pinout will be interesting.

    Another thought: does this list as HD for engine ? Using linear EGR etc.
    They used to call the 4L80E's the HD trans.
    About 4 kinds of "HD" possible on same truck,
    GM keeping things simple and all.
    HD? I unfortunately can not tell you as this is highly confidential information. No really it's hard to say. Non original block, re-manufactured heads, no glove box RPO information readable. It has the 8600 GVWR, 8 lug, 14 bolt rear end and big 34" core radiator with both side coolers(non HD cooling system as far as I am aware).

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