Question about 1994 Pontiac Bonneville

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OBD 1 and 2 will not communicate with PCM.

I have a '94 Pontiac Bonneville SE. The car starts and will sometimes idle (rough) and stall, Idle OK but after fluctuating throttle will maintain a high idle (About 3000 RPM manifolds go Cherry). All occur while in Open Loop. Closed Loop, sometimes will drive fine and then intermittently stall at idle and or stall continuosly closed throttle/ at idle.
The car is a OBD 2 phase in. OBD connector is "wedge side" (OBD 2) but the emmission label does not designate this vehicle as OBD 2. OBD 1 and 2 interface will not communicate with PCM. Check engine lamp will illuminate in Closed Loop.
How can codes be accessed? Is PCM OBD inoperative? I have '93 Bonneville GM Shop manuals. Are systems similar enough to use OBD fuction diagnosis by referencing wire color @ OBD connector?
GM should have left good enough alone and stuck with engine light code display!

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  • m_hanks66 Nov 13, 2008

    What old system? I purchased my first interface tool in 1984, called a Monitor 84. This was no different from the current interface scanner I used, an Innova OBDI/II new model. After investigating the capabilities further, this OBD tool does not have the capability to work on this model/year.

    You did not understand my comment. Since the inception of onboard diagnostics/GM's CCC system and up until '93 model year you were able to extract the ECM (PCM) and BCM codes with only the paperclip. A high impedance multimeter, test light, jumper wires and a GM shop manual are all that were (are) necessary to diagnose and repair emission/body control systems. The shop manuals symptom, trouble shooting and diagnostic charts/tables are, and will always be, intended to be a Techs main tool. The information/functions an on board computer provides/controls has basically not changed. The emission controls/sensors/methods have. My point is, rather than extracting codes simply and economically, this change to the OBD tool interface requirement requires one to borrow or purchase the Tool to accomplish this simple task. The interface tools are simply convienient and allow real time reading and contol activation capabilities. The Cadillac, Toronado, Riviera O.B.D. systems that allow interface via the climate control systems was a "good" idea. No "special" tools required there and have/had all the capabilities of any of the available interface monitors.

    So, sorry not wrong. As I stated earlier, the cars system is not designated OBDII because this would be exhibited on the emissions label. The interface connector is non OBD I because it is not rectangular but has angled sides like OBD II. It falls in an interface period between I and II, unfortunately.

    I thought maybe someone else may have ran into a similar issue. I did confirm the fuses/power supplied in the diagnostic system is OK. Maybe the PCM is blown? I guess my best bet will be to get access to this model years service manual.

    Thanks for your help. Any other ideas would be welcome.

  • yadayada
    yadayada May 11, 2010

    I have no idea what you talking about, OBD 1 started in late 83, very poor system, very little self diagnostics like OBD 2

  • yadayada
    yadayada May 11, 2010

    You are wrong, the OBD 2 system is far superior in every way to the old system, no you can't access it by using the CEL but the scanner does a much better job. Are you sure this is OBD 2?

  • Anonymous Mar 31, 2014

    OBD code P0410


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I have the exact same problem with my 94. I would like to know what you did to fix it. Please help.

Posted on Mar 20, 2013

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You are describing exactly what a lot of 94-95 GM car owner are feeling. I have an AUtoXray6000 scanner and it can read the trouble codes on this car, (I have a 95 Bonneville) but wont read the data stream. Basically you have a OBDII plug, but the car is controlled by the same OBDI system as others prior to 96. There are some scanners that have the ability to read the codes and data stream on these cars, others can only read the codes. If you can get or design an interface cable plug and know how to route the wires, you're in like flynt. Here is a web site that makes parts for a conversion cable..

Posted on Feb 06, 2009

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A blown fuse will also cause the obd to not communicate

Posted on Nov 12, 2008

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