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Car dies PCM replacement ?


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Hello,

Commonly when I start my car the SES light never cycles on, and rarely does it come on with the key turned on. I was wondering why ? I have spent sometime now looking around online. The same thing happens when trying to access the DIC. I have IMP B0249 and IPM B0429 on all the time since I bought the car.The car when coming to a stop light will die and sometimes does a power down shift it seems. I have replaced the IAC and the map sensor. This seems to only fix it for a short time and then it's back to dying. It also seems that with the weather warming and cooling that this plays some effect on it and when it is colder it seems to run better.

Please Help,

Michael-

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The B0249 indicates a mode actuator in the A/C unit is having an issue. This is unlikely to keep the engine from running.

The car when coming to a stop light will die and sometimes does a power down shift it seems

Dying at a stoplight makes me think fuel pressure regulator.

DTC B0249

Circuit Description

The mode actuator is an electronic stepper motor. The HVAC control module (IPM) supplies power and ground to the actuator. The IPM controls the direction of the mode actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value (9.5 to 12 volts). The IPM determines the door position by counting pulses (voltage fluctuations) caused by the brush to commutator action generated during normal motor operation. The IPM monitors a voltage drop across an internal resistance to detect the pulses. The IPM converts the pulses to counts with a range of 0 to 255 counts.

When a calibration or recalibration procedure is performed, the IPM calculates the mode door travel range. The IPM commands the actuator to each extreme position and counts the total number of pulses. The IPM compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful.

Conditions for Running the DTC

The IPM will run the DTC when either of the following conditions are met.

* The IPM has completed a calibration/recalibration of the mode actuator.

* The IPM commands the actuator to move.

Conditions for Setting the DTC

The IPM will set this DTC if either of the following conditions are true.

* The mode actuator fails calibration/recalibration due to an over travel or under travel condition. (The IPM does not detect the calibrated number of total pulse counts during a travel range check.)

* The IPM determines that the actual door position does not equal the commanded door position. (The IPM commands the door to move but does not see the expected number of pulses between positions.)

Action Taken When the DTC Sets

* The IPM will attempt to make use of whatever range is still available.

* The IPM will recalibrate the mode actuator each time the ignition switch is turned ON.

Conditions for Clearing the MIL/DTC

* The DTC will become history if the IPM no longer detects a failure.

* The history DTC will clear after 50 fault free ignition cycles.

* The DTC can be cleared with a scan tool.

Diagnostic Aids

* Inspect the mode door and mode actuator for the following conditions:

o A misaligned mode actuator. Refer to Mode Actuator Replacement .

o Broken or binding linkages or mode door

o Obstruction that prevents the mode door from operating within its full range of motion

o Missing seals to the mode door

o Misaligned seals to the mode door

* Refer to Testing for Intermittent and Poor Connections in Wiring Systems.

Bruce

2023 Cadillac CT4-V Blackwing

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Hmmm good stuff! My main concern was why the SES light doesn't cycle though ? It just seems strange to me that it rarely comes on.. . Am I making a big deal out of nothing ? LOL Sometimes I get high idol codes and with random U1016 codes.. When I had my IAC unit replaced the shop seemed to had wondered if the PCM was going bad. I have read a lot about ground issues though.

Thanks,

Michael-

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Also today I got a high idol code of P0507.. The throttle likes to sick and the rpm's go up to 1000-12000 when trying to bring the car to a stop again doing this strange power down shifting . Sometimes the car will not start with out giving it a little gas.. UGH..=(

Michael

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