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Thread: New Here -- Looking Forward To Learning

  1. #1
    Carb and Points!
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    New Here -- Looking Forward To Learning

    Hi everyone, this site is proof that good things can happen when you're searching for a solution to an error code! We've been chasing a Code 21 (TPS) on a 1991 Buick Riv, and unless we have a nasty vacuum leak that we've been unable to find, then our best guess is that the MEMCAL is fried. All the wiring is 100% as to the usual (continuity, volts, amps) and based on those tests, the Buick Service Manual Diagnostics said the ECM should be replaced. We did that. Of course we swapped over the EPROM/MEMCAL. The car runs great but the error code remains and is driving us crazy. We're about to install Tuner Pro on a laptop and try that for diagnostics, but does anyone know how to tell if the MEMCAL itself is causing the problem? Thanks!

  2. #2
    EFI GearHead ! EagleMark's Avatar
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    Check the voltage at TPS. From idle around .54 volts to WOT 4.5 Volts + Should be a slow smooth sweep.


    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  3. #3
    Carb and Points!
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    Quote Originally Posted by EagleMark View Post


    Check the voltage at TPS. From idle around .54 volts to WOT 4.5 Volts + Should be a slow smooth sweep.

    Hey thanks! Did all that weeks ago. Static Test (ign on): With a voltmeter black (grd) to battery positive reads 12.6v. Gray (SV reference) to black reads 5v. But here's the crazy damn thing that nobody seems able to explain:

    The BLUE wire (TPS Signal) reads a minimum of 2.62 volts when it should be reading .33 to .46 with closed throttle.

    Based on this we pulled the old TPS and bench tested a new A.C. Delco TPS, and from the bench the signal and roll is perfect.

    Before installing we did a continuity test (and resistance) on all three wires from the harness connector all the way back to the ECM, and all the wires are clean and tight, as is the connection.

    When we continued to get a 2.62 or even higher signal from the Blue TPS Signal wire, we decided to replace the ECM and...

    ...nothing changed. The Blue TPS Signal still reads a minimum of 2.62 volts with clean connections and a new ECM.

    We're in the process of installing Tuner Pro so that we can get inside the system and start reading, but WOW! How can anyone not laugh at this: we're in Scottsdale, Arizona, and right now the outside temp is 104, and that's big cool down for us. This old Riv has an amazing R12 AC unit that blows 11-degrees at the pipe, drops the inside to 62, but because we can't get through emissions -- I'm driving an ALL BLACK Firebird with friggin 134A that gets so damn hot I have to wear a winter glove to shift.

    So do you think we could have a memory control, i.e., Memcal, that has fried or developed a nasty sense of humor? Lol. Idaho sure sounds nice!

  4. #4
    Fuel Injected! gregs78cam's Avatar
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    It sounds like you have another wire crossed with that TPS signal wire......with TPS unplugged what do get on the signal wire at the connector?
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  5. #5
    Carb and Points!
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    Need A Little Help In The Heat...

    Quote Originally Posted by gregs78cam View Post
    It sounds like you have another wire crossed with that TPS signal wire......with TPS unplugged what do get on the signal wire at the connector?
    Hey, thanks for the thought. Seriously, that made us paranoid again, so we checked the wires again and ran a continuity test. The TPS Signal wire is solid, no shorts, no cross, and so we're trying to get TunerPro up and running. If somebody could lend some advice on that, we sure would appreciate it.

    The engine is a 1991, 3800, Vin Code L, RPO L27 with ECM P/N 16141470.

    To make TunerPro work we searched and downloaded XDF "$5B3 91 Buick-Pontiac L27 3800," and for streaming we downloaded "A112.DS," which I guess we have to convert to .ADX using TunerPro.

    We're pretty sure that leaves us with only the BIN to find, which we saw listed as "$5B3" but then we're wondering about an unclear reference that suggests using .XDF for BIN?

    Confusing if you've never dealt with these before.

    So what should we be looking for regarding the BIN and where would we find that, nothing has come from our many searches?

    Thanks.

    Yup, forgot to check the actual volts at the wire, 101 outside, no kidding. We went running for the AC and I think that will be tonight's low? Lol.

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