2010 cobalt 2.2 reduced engine power

[Topher5228]

Ok I have resorted to the cobalt forum after pulling my hair out. I have a 2010 chevy cobalt basic package 2.2L. 69k. I'm having issues with reduced engine power/engine disabled with a code p0641 which is the 5 volt reference. The funny thing is it only happens when it's cold and now it's winter and always cold it's happening more frequently. I've replaced the ecm, new battery, removed throttle body and cleaned checked all grounds and cleaned. Checked harnesses for exposed wires, tested sensors with a multimeter a checked all connections. Has anyone had to deal with this ridiculous issue?? ?

Thanks for any input!

 

[roosterk0031]

My daughters 2010 had a temperature related problem. When it got below freezing, the hazards would start flashing till it ran the battery dead. Next day I installed my battery it started right up and she drove it home for thanksgiving. That afternoon it got cold and lights started flashing again. I disconnected the battery. 3-4 days later it got warm, connected battery all good got it home. Middle of night knock on door lights flashing again, disconnected battery. Next morning I put a electric heater next to the BCM, gave it 20 minutes, connected battery everything fine. $600 and a new BCM fixed it, must have been just over 2 years ago.

 

[roosterk0031]

Oh when I left at the dealer they left it outside and I disconnected the battery, they said they were able to wiggle the BCM wiring to get it to start the next morning without doing the heater trick.

 

[Topher5228]

Oh when I left at the dealer they left it outside and I disconnected the battery, they said they were able to wiggle the BCM wiring to get it to start the next morning without doing the heater trick.

When the dealer replaced the ecm they said they checked the communicating modules and everything checked out fine. It's not having issues starting at all it starts but when it's cold the p0641 code comes on with the engine power reduced and if you drive it for a couple minutes the car disables the engine and stalls it out. You turn the key off wait a couple minutes and starts and drives like nothing is wrong.

 

[YelloEye]

Some diagnostic help for you and that code. You probably have a wire or component shorting high or low.

Circuit/System Description
The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference buss provides 5-volt reference circuits for more than one sensor. A fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference buss. The ECM monitors the voltage on the 5-volt reference buss.

The 5-volt reference 1 buss provides 5 volts to the following sensors:

• The manifold absolute pressure (MAP) sensor

• The fuel tank pressure (FTP) sensor

• The air conditioning (A/C) refrigerant pressure sensor

• The accelerator pedal position (APP) sensor 2

• The exhaust camshaft position (CMP) sensor

• The intake CMP sensor

The 5-volt reference 2 buss provides 5 volts to the following sensors:

• The APP sensor 1

• The throttle position (TP) sensor 1 and 2

• The crankshaft position (CKP) sensor

Diagnostic Aids
It may be possible to locate the fault by disconnecting one component at a time from the 5-volt reference circuit while viewing the 5-Volt Reference circuit parameter on the scan tool. The scan tool parameter would change from Fault to OK when the source of the fault is disconnected.

If all 5-volt reference components have been disconnected and a Fault is still indicated, the fault may exist in the wiring harness.

Circuit/System Testing
Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC.
Note: A short to voltage on the signal circuit of certain components may cause this DTC to set.

Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
⇒ If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the ECM.

⇒ If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits. If all circuits test normal, replace the ECM.

Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. Verify the voltage remains between 4.8-5.2 volts.
⇒ If the voltage display is not within the specified range when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the component.

 

[Topher5228]

Ok so here is an update. After a lot of time of diagnosis of the electrical system and sensors the culprit was the Fuel Tank Pressure Sensor (FTPS). The sensor was sending fluctuations of voltage to the ecm causing the P0641 5 volt reference code. Simply unplugged the sensor and car returned to normal minus the check engine light illuminated (obviously). But all in all goes to show never give up and the self satisfaction of figuring out an issue the dealership couldn't is worth it.

 

[Lsully]

Okay I need some help guys! I have a 2010 Cobalt and my battery light has been on for a month or so. I kinda bluffed it off cause I didnt have the time to fix it cause I'm always working. Anyways, the other day my engine light popped on and said reduced engine power and service traction. I had my dad scan it and it gave me the p0641 code which refers to the 5 volt circuit 1 reference. Before I go replacing any sensors... Do you think this could be caused because of my original issue which was the battery needing to be replaced or no?

I'm thinking I should start with buying a new battery to see if it will charge the alternator enough to fix the issue because that may be triggering the sensors and reducing my cars performance. Any thoughts would really help