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Service traction control light is on

Tiny
BHSHOOT
  • MEMBER
  • 2008 CHEVROLET COBALT
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 132,000 MILES
My ob11 reader says it is the crankshaft position sensor. So, I got a new one and replace it. This did not help. Cars starts hard also shifts slow. Works okay feels like limp mode. The speedometer works, but the tachometer doesn't. I need help! I have traced the wire through the crankshaft sensor and they all seem okay. I even traced the voltage to the crank sensor and it seems okay also. Ie 5.5 volts. Just a thought could it have something to do with the input or output sensor on the transmission?
Any advice would help. I am not a mechanic but I do all my own work because I am cheap, lol. Thanks in advance.
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Tuesday, January 22nd, 2019 AT 10:31 AM

8 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Lets start with the code numbers. Codes rarely identify failed parts just failed systems.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Were there any codes for the ABS system as well? The traction system is controlled by the ABS.

https://www.2carpros.com/articles/abs-warning-light-on-easy-repair-guide

Roy
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Tuesday, January 22nd, 2019 AT 11:43 AM
Tiny
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Hey Roy,
There is no ABS light on, it did come on one day when I unhooked the battery for a bit. It stayed on for about a mile and went out again. Never came on since. The codes that my ob11 reader are as follows: Pere:00
PO335
PO651
PO335 Pd
That is all. It is just confusing because my tachometer stopped working the same time the service traction control came on. This is every thing I know. All connections and wires seem fine. I traced a lot of them for continuity. I do not know where to go from here. Appreciate any help at this time. Thank you for your prompt reply.
Maybe this will shake your brain up too. Lol
.
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Tuesday, January 22nd, 2019 AT 12:15 PM
Tiny
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Sorry, I never mentioned it is an automatic. If that matters.
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Tuesday, January 22nd, 2019 AT 12:35 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, the 651 is my concern as it is a loss of the 5 volt reference signal. That is critical for all the codes.

This voltage comes from the PCM.

P0641: 5V Reference 1 Circuit
P0651: 5V Reference 2 Circuit

Related Vehicles: 2008 - 2010 Cobalt, G5, 2.2L

Notes/Hints:

P0641: Affected Components;
Manifold Absolute Pressure (MAP) Sensor
Fuel Tank Pressure (FTP) Sensor
A/C Refrigerant Pressure Sensor
Accelerator Pedal Position (APP) Sensor 2
Exhaust Camshaft Position (CMP) Sensor
Intake Camshaft Position (CMP) Sensor
P0651: Affected Components;
Accelerator Pedal Position (APP) Sensor 1
Throttle Position (TP) Sensors 1 and 2
Crankshaft Position (CKP) Sensor
Air Injector Reactor (AIR) Pressure Sensor (if equipped)
Clutch Pedal Position Sensor (if equipped)
Use the 5-Volt and Low Reference Bus wiring diagrams for specific components.
Preliminary Tasks:

Follow the latest TSB recommendations.
Verify the scan tool and ECM have the most up-to-date software and calibrations installed.
Perform a close visual inspection of the affected components, wire harness and connectors.
Disconnect and inspect the ECM and affected components, harness connectors for any moisture or poor connections. Apply dielectric grease and reconnect.
Diagnosis:

1. Verify the reference voltage between one of the affected components and ground is between 4.8†5.2 volts.
--> If the reference voltage is between 4.8†5.2 volts, the condition is not present.
--> If the reference voltage is NOT between 4.8†5.2 volts, proceed to the next step.

2. Disconnect the affected components one at a time until the reference voltage is between 4.8†5.2 volts.
--> If all components are disconnected and the reference voltage is not correct, disconnect the ECM.
--> If the reference voltage is NOT correct with ECM disconnected, repair the short to voltage or ground in the reference circuit.
--> If the reference voltage is correct with ECM disconnected, replace the ECM.

This is a possible PCM failure or a wiring harness issue. The wiring will need to be checked to verify.

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

Roy
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Tuesday, January 22nd, 2019 AT 12:37 PM
Tiny
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Automatic does not matter.

Roy
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Tuesday, January 22nd, 2019 AT 12:52 PM
Tiny
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Wow, I think I will drive as is until it stops. Too much for a guy with no garage. It is twenty below and nothing but snow for the next couple of months. Thank you for your help. I thought it may be worse than what I thought. Easy question, what controls the tachometer? If I do figure this out, I will let everyone in on it. Thanks
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Tuesday, January 22nd, 2019 AT 1:10 PM
Tiny
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I do not understand the first diagnostic part what affected components am I to check all of the sensors for the code 651 or just the crank sensor. If so am I to have the car running or just the key turn on? What if I get a lower or higher reading than just 4.8-5.2 volts? Again part 2 all of the components is this just under the code 651. I am confused but this is normal. Thanks again
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Tuesday, January 22nd, 2019 AT 1:24 PM
Tiny
ASEMASTER6371
  • MECHANIC
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The tachometer is controlled by the PCM.

The normal reference voltage is 5 volts. That's what you need.

Roy
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Tuesday, January 22nd, 2019 AT 2:04 PM

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