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1999 Mazda Protege Question: Over drive light blinking, check engine code PO123

 

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Visitor, 1.6L 4 Cylinder, Averill Park, NY, January 09, 2011, 19:49

The check engine light came on and the the Overdrive light began blinking. The car would only go to 2nd gear (auto). Scanner showed code PO123, Throttle postioning sensor, High voltage A circuit. Took to a garage put on ocm scanner, same thing. Bought new Napa TPS. Now the Over-drv light doesn't blink at idle, only when you accelerate. Car shifts to 3rd gear but doesn't shift until high rpm. Swapped conputer, still the same. Is it possible I got a "bad" new sensor.

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  • Medium-star Best Answer
    DaveJHM January 09, 2011, 20:03
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     Master

    No, it's more likely you have additional problems. The TP sensor really shouldn't affect the overdrive light at all. The O/D light blinking is indicative of a transmission fault. There should be additional codes other than the P0123. Swapping a computer should also do nothing for you. Recommend having a good diagnosis performed. I think you will end up having something occuring internally with a transmission solenoid or something of that nature.

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    Visitor, January 09, 2011, 21:20

    I appreciate the reply, but I have an actron scanner myself. There were no other codes. I reset the car, tried to drive an got immediate Check engine light and blinking Ovr dr indicator. I took the car to one of my mechanics's shop and he put his big scanner on it. Only got the one code. Suggested that I get a new TPS. When I installed it, the blinking Ovr-drv indicator became "intermittent" doesn't do it when the car is at idle. I'm close friends with a salvage yard and their main mechanic. Thats why we tried the computer swap, just to see if there was an issue. The car has had no problems with the tranny. Idle is smooth. For the hell of it, I put the old TPS back in and the situation deteriated back to the original problems, so the TPS has something to do with it. Thank You anyways, this is pretty frustrating.

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    DaveJHM, January 09, 2011, 22:04
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     Master

    I look at troubleshooting from a perspective of understanding fundamental operation and then what possible causes of malfunction are.

    The O/D light could flash because of shifting not occuring as expected, which could be from a TP sensor issue I suppose. You would agree that there obviously must still be something failing since there is still a shifting issue and still a flashing O/D light.

    Here is the shop manual instruction for P0123 diagnosis. This way you can verify the system is working properly.

    DTC P0123 TP circuit high input

    DETECTION CONDITION

    Input voltage from TP sensor is above 4.8 V and ignition switch is ON.

    POSSIBLE CAUSE

    TP sensor malfunction
    Short to power supply circuit in wiring from TP sensor terminal B to PCM terminal 91
    Short to power supply circuit in wiring from TP sensor terminal A to PCM terminal 90
    Short to power supply circuit in wiring from TP sensor terminal C to PCM terminal 89
    Open circuit in wiring from TP sensor terminal B to PCM terminal 91
    Open circuit in wiring from PCM terminal 24, 51, 76, 77 and/or 103 to negative battery terminal


    STEP 1
    VERIFY FREEZE FRAME DATA HAS BEEN RECORDED

    Has FREEZE FRAME DATA been recorded?
    Yes
    Go to next step.

    No
    Record FREEZE FRAME DATA on repair order, then go to next step.

    2
    VERIFY PENDING CODE AND STORED DTC

    Have DTCs P0108, P0113, P0118, P0134 and/or P0453 been stored?
    Yes
    Inspect for open or short circuit to power supply circuit in following wiring harnesses, repair faulty areas, then go to Step 9.

    From PCM terminal 91 to EGR boost sensor, IAT sensor, ECT sensor, front HO2S, and/or fuel tank pressure sensor

    From PCM terminal 24, 51, 76, 77 and/or 103 to negative battery terminal


    No
    Go to next step.

    3 INSPECT TP SENSOR POWER SUPPLY CIRCUIT FOR SHORT TO POWER SUPPLY CIRCUIT

    Turn ignition switch off.

    Disconnect TP sensor connector.

    Turn ignition switch on.

    Is there 5 V at harness side connector terminal A?
    Yes
    Go to next step.

    No
    Inspect for short to power supply circuit in wiring harness and/or connector between TP sensor harness side connector terminal A and PCM harness side connector terminal 90, repair faulty areas, then go to Step 9.

    4 INSPECT TP SENSOR GROUND CIRCUIT FOR OPEN

    Turn ignition switch off.

    Leave TP sensor connector disconnected.

    With PCM connector disconnected, install breakout box.

    Is there continuity between TP sensor harness side connector terminal B and test pin 91?
    Yes
    Go to next step.

    No
    Repair open circuit, then go to Step 9.

    5 INSPECT TP SENSOR GROUND CIRCUIT FOR SHORT TO POWER SUPPLY CIRCUIT

    Leave breakout box installed.

    Leave TP sensor and PCM disconnected.

    Is there continuity between test pin 91 and test pin 71, 97?
    Yes
    Repair short to power supply circuit, then go to Step 9.

    No
    Go to next step.

    6
    INSPECT TP SENSOR SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY CIRCUIT

    Leave breakout box installed.

    Leave TP sensor and PCM disconnected.

    Is there continuity between test pin 89 and test pin 71, 97?
    Yes
    Repair short to power supply circuit, then go to Step 9.

    No
    Go to next step.

    7 INSPECT TP PID FOR CHANGE ACCORDING TO THROTTLE VALVE OPENING ANGLE

    Remove breakout box.

    Connect TP sensor and PCM connectors.

    Connect NGS tester to DLC‐2.

    Turn ignition switch on.

    Access TP V PID.

    Does TP V PID increase liner according to throttle valve opening?
    Yes
    Go to next step.

    No
    Replace TP sensor, then go to Step 9.

    8
    VERIFY TROUBLESHOOTING OF DTC P0123 COMPLETED

    Clear DTC from memory.

    Is same code No. present after performing After Repair Procedure?

    » 01-01A ENGINE ON-BOARD DIAGNOSTIC [ZM], After Repair Procedure [ZM]
    Yes
    Refer to related Service Bulletins and/or on-line repair information and perform repair or diagnosis.

    •If vehicle is repaired, troubleshooting completed.

    •If vehicle is not repaired or additional diagnostic information is not available, replace or reprogram PCM.

    Then go to next step.

    No
    Intermittent poor connections of harness or connector.

    Repair connector and/or harness, then go to next step.

    9
    VERIFY TROUBLESHOOTING COMPLETED

    Clear DTC from memory.

    Is there any code No. present after performing After Repair Procedure?

    » 01-01A ENGINE ON-BOARD DIAGNOSTIC [ZM], After Repair Procedure [ZM]
    Yes
    Go to applicable DTC inspection.

    No
    Troubleshooting completed.

    Regarding the O/D light - From the shop manual:

    "The O/D OFF indicator light flashes when any malfunction exists in the EC‐AT system components."

    Hope this helps. Good luck.

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    Visitor, January 10, 2011, 04:17

    New developments... I took the car to a facility that has a breakout box and he reported the "new" TPS to be reporting the wrong voltage at idle. He called the aftermarket sales rep and stated that the application is incorrect. A factory OEM has been ordered and will be installed on Thursday. We'll see what happens.

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  • Answer #2

    patrick mannion from Greg Solow's Engine Room, January 09, 2011, 22:10
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     Master

    Look a wiring diagram, use an OHM meter to do a continuity check at the computer to ensure the wiring is good from the TPS back to the computer, just had similar problem with a Toyota ended up wire at TPS was broken at the connector at switch.
    Autozone have some popular workshop manuals for free on line once you register (for free) on their website http://bit.ly
    /autozone_repair_info or there is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You can get a one week subscription or year subscription very cheap. The information is year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual try http://bit.ly/mitchell_repair_manuals_online
    and get an online repair manual subscription.

    Dave just saw your answer, great answer!

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    Visitor, January 10, 2011, 04:23

    Started going thru Mazda procedure. Voltage at tps "supply" is 5.04 volts. Disconnecting the plug at the tps, there is continuity from the middle "ground" terminal in the connector. (Test lite lites when hooked between +bat terminal and said ground wire. Code is verified and only one reading (PO123). During this time I found if the connetor to the tps is disconnected, the Ovr drive indicator blinks constantly. I don't have a 104 pin breakout box so tomorrow I'm going to a mechanic who does. Also checked for continuity from the connector to the engine block off the middle (ground ) wire. I have continuity. Guys, I'm trying...Thanks for the help again. Chris

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