Engine power reduced coming on

Tiny
DARROL WADE
  • MEMBER
  • 2009 CHEVROLET COBALT
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 67,000 MILES
I am getting engine power reduced coming on. I had it to the dealer and was told it was fuel tank pressure sensor. I put a new one in and still have same problem. Any suggestions?
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Friday, January 4th, 2019 AT 1:46 PM

11 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

What was the exact code?

Reduced power is from either the TPS or pedal sensor malfunction.

Roy

The engine control module (ECM) is the control center for the throttle actuator control (TAC) system. The ECM determines the driver's intent based on input form the accelerator pedal position sensors, then calculates the appropriate throttle response based on the throttle position sensors. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the throttle actuator motor. The throttle blade is spring loaded in both directions, and the default position is slightly open.

Modes Of Operation

Normal Mode

During the operation of the TAC system, several modes, or functions, are considered normal. The following modes may be entered during normal operations:

* Minimum pedal value-At key-up, the ECM updates the learned minimum pedal value.
* Minimum throttle position values-At key-up, the ECM updates the learned minimum throttle position value. In order to learn the minimum throttle position value, the throttle blade is moved to the Closed position.
* Ice break mode-If the throttle blade is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the ECM commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
* Minimum pedal value-At key-up, the ECM updates the learned minimum pedal value.
* Battery saver mode-After a predetermined time without engine RPM, the ECM commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode

When the ECM detects a condition with the TAC system, the ECM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:

* Acceleration limiting-The ECM will continue to use the accelerator pedal for throttle control, however, the vehicle acceleration is limited.
* Limited throttle mode-The ECM will continue to use the accelerator pedal for throttle control, however, the maximum throttle opening is limited.
* Throttle default mode-The ECM will turn OFF the throttle actuator motor, and the throttle will return to the spring loaded default position.
* Forced idle mode-The ECM will perform the following actions:

- Limit engine speed to idle positioning the throttle position, or by controlling the fuel and spark if the throttle is turned OFF.
- Ignore the accelerator pedal input.

* Engine shutdown mode-The ECM will disable fuel and de-energize the throttle actuator.
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Friday, January 4th, 2019 AT 2:00 PM
Tiny
DARROL WADE
  • MEMBER
Thanks here are the codes that were checked: checked DTCs; P0561, P0532, P0455, P0107, P0106, P2270, P0141, P0054, P0036 set in ECM. Vehicle going into reduced engine power at times. Suspect fuel tank pressure sensor shorting out taking down 5 volts reference circuit 1. This is what the printout said. I am wondering could it be the MAP sensor?
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Friday, January 4th, 2019 AT 5:48 PM
Tiny
ASEMASTER6371
  • EXPERT
Yep, lots of 5 volt reference issues.

Pull the TPS connector and check for a 5 volt reference signal with the key on. Wondering if the PCM is the issue as it sends the voltage from there.

Roy

Example 532

P0532
Descriptor
Probable Causes
5-Volt Reference Circuit Open or High Resistance
5-Volt Reference Circuit Short to Ground
A/C Refrigerant Pressure (ACP) Sensor
A/C Refrigerant Pressure (ACP) Sensor Signal Circuit Short to Ground
A/C Refrigerant Pressure (ACP) Sensor Signal Circuit Short to Voltage
Engine Control Module (ECM)
Low Reference Circuit Open or High Resistance
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Friday, January 4th, 2019 AT 6:00 PM
Tiny
DARROL WADE
  • MEMBER
Is the PCM the computer?
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Friday, January 4th, 2019 AT 6:30 PM
Tiny
ASEMASTER6371
  • EXPERT
Correct.

Roy
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Friday, January 4th, 2019 AT 6:45 PM
Tiny
DARROL WADE
  • MEMBER
How much to replace?
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Friday, January 4th, 2019 AT 6:47 PM
Tiny
ASEMASTER6371
  • EXPERT
If that is the problem, the computer is about $200.00. I posted the part below.

https://www.rockauto.com/en/catalog/chevrolet,2009,cobalt,2.2l+l4,1442864,electrical,engine+control+module+(ecm+computer),2896

The labor is one hour or about $100.00.

The flash programming is around $150.00.

You need to have this verified first. make sure there is no wire harness issue or you may damage the new module after installed.

https://www.2carpros.com/articles/how-to-check-wiring

Roy
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Saturday, January 5th, 2019 AT 3:21 AM
Tiny
DARROL WADE
  • MEMBER
Thanks Roy.
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Saturday, January 5th, 2019 AT 7:00 AM
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Always glad to help.

Roy
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Saturday, January 5th, 2019 AT 7:18 AM
Tiny
AUSTIN ALLISON
  • MEMBER
Roy I have a 2007 Cobalt with 2.0 just put a new clutch in and drive it over to a alignment shop and now it won’t start. Tried to pop start it and nothing. Now when I turn the key on it don’t turn over or anything. All I can hear is relays clicking and a light comes on the dash says engine power reduced.
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Wednesday, October 16th, 2019 AT 9:43 AM
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

I would be glad to help you but you need to start a new question at the beginning.

Roy
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Wednesday, October 16th, 2019 AT 10:54 AM

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