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post #1 of 4 (permalink) Old 08-15-2017, 11:06 PM Thread Starter
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2010 Cobalt Code P0641 Engine Power Reduced

Hey I'm new to this and I really need your help, like we all do lol.
Listen my son has a 2010 cobalt with a 2.2 engine and the car has a code p0641 only and engine power reduced on the dash. They told him at Autozone that the car needs the fuel tank pressure sensor. Doing some research and I see that it has to do with 5 volts reference and I also see that it has to do with like 4 other sensors too. I really don't know how they new that it's the ftps. But any insight would be appreciated like wiring diagrams, from like pcm/ecm the location of it and anything else would help and thanks in advance.

I've looked at the other posts and didn't help!
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post #2 of 4 (permalink) Old 08-16-2017, 07:37 AM
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P0641 5-Volt Reference 1 Circuit ECM

This code refers to ECM 5Volt circuit 1, which is to the left on the diagram. I don't know how he could tell that it was the fps because this code only says that 5V1 was lost or out of range for more than 3 seconds. It could be the MAP or a frayed wire along the back side of the valve cover or possibly just a burnt fuse. The ECM will set the first code on it's list and if it's an A code will proceed to put vehicle into limp mode and stop scanning for more codes.



DTC P0641-P0643
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC P0641: 5-Volt Reference 1 Circuit

DTC P0642: 5-Volt Reference 1 Low Voltage

DTC P0643: 5-Volt Reference 1 High Voltage

DTC P0651: 5-Volt Reference 2 Circuit

DTC P0652: 5-Volt Reference 2 Low Voltage

DTC P0653: 5-Volt Reference 2 High Voltage

DTC P0697: 5-Volt Reference 3 Circuit

DTC P0698: 5-Volt Reference 3 Low Voltage

DTC P0699: 5-Volt Reference 3 High Voltage


Diagnostic Fault Information
Circuit
Short to Ground
Open/High Resistance
Short to Voltage

Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference 2 Circuit
P0652
P2122
P0653

Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference 3 Circuit
P0698
P2127
P0699

Air Conditioning (A/C) Refrigerant Pressure Sensor 5-Volt Reference 3 Circuit
P0698
P0532
P0699

Crankshaft Position Sensor 5-Volt Reference 3 Circuit
P0698
P0335
P0699

Engine Oil Pressure Sensor 5-Volt Reference 3 Circuit
P0698
P0520
P0699

Exhaust Camshaft Position Sensor 1 5-Volt Reference 2 Circuit
P0652
P0368
P0653

Fuel Rail Pressure Sensor 5-Volt Reference 1 Circuit
P0642
P0192
P0643

Fuel Tank Pressure (FTP) Sensor 5-Volt Reference 1 Circuit
P0642
P0452
P0643

Intake Camshaft Position Sensor 1 5-Volt Reference 2 Circuit
P0652
P0343
P0653

Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit
P0642
P0107
P0643

Throttle Position (TP) Sensor 1 5-Volt Reference 3 Circuit
P0698
P0122
P0699

Throttle Position (TP) Sensor 2 5-Volt Reference 3 Circuit
P0698
P0222
P0699

Intake Air Pressure and Temperature Sensor 5-Volt Reference 1 Circuit
P0642
P0238
P0643


Circuit/System Description
The engine control module (ECM) has 3 internal 5-volt reference busses called 5-volt reference 1, 5-volt reference 2, and 5-volt reference 3. Each reference bus provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference bus. The ECM monitors the voltage on the 5-volt reference busses.

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

The manifold absolute pressure (MAP) sensor

The clutch apply sensor

The fuel rail sensor

The fuel tank pressure (FTP) sensor

The intake air pressure and temperature sensor

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

The accelerator pedal position (APP) sensor 1

The exhaust camshaft position (CMP) sensor

The intake camshaft position (CMP) sensor

The 5-volt reference 3 bus provides 5 volts to the following sensors:

The APP sensor 2

The crankshaft position (CKP) sensor

The air conditioning (A/C) refrigerant pressure sensor

The throttle position (TP) sensor 1 and 2

The brake booster vacuum sensor

Conditions for Running the DTC
DTCs P0601, P0602, P0603, P0604, and P0606 are not set.

The ignition is in Run, or Crank.

The ignition voltage is more than 5.23 volts.

DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 run continuously when the above conditions are met.

Conditions for Setting the DTC
P0641, P0651, and P0697

These DTCs set when the ECM detects a voltage out of tolerance condition on the 5-volt reference 1, 2 or 3 bus for more than 3 seconds.

P0642, P0652, and P0698
These DTCs set when the ECM detects a low voltage condition on the 5-volt reference 1, 2, or 3 bus for more than 3 seconds.

P0643, P0653, and P0699
These DTCs set when the ECM detects a high voltage condition on the 5-volt reference 1, 2, or 3 bus for more than 3 seconds.

Action Taken When the DTC Sets
DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 are Type A DTCs.

Conditions for Clearing the DTC
DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 are Type A DTCs.

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.

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post #3 of 4 (permalink) Old 08-16-2017, 08:31 AM Thread Starter
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Hey thanks coby7, my scanner told me the map sensor as a repair but you know how that goes it's a suggestion that it gives you lol. I'm going to look at the huge favor you doing for me cause my son started a new job on Monday and the car started to act up on Sunday night. I have to take him to and from one hour drive. And that sucks lol, yeah cause the car went into a limp mode and he couldn't drive more than 35 mph. So I hope I can figure this out quickly so I don't have to go thru this driving lol, so thanks again and let me go to work and i will come back with input on what happened.
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post #4 of 4 (permalink) Old 08-18-2017, 12:58 AM Thread Starter
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Hey coby7 thanks for the help. I asked my son why the car smelled like coffee and he told me that he was doing uber Sunday night and a passenger had asked him if he can open the trunk to put the suit case inside and when he opened it she quickly put the suit case in, my son was going to put it in for her. The thing is that she had a big pot of coffee ready to drink and the whole thing spilled in the trunk so after I was running test i jacked up the car and found 2 connectors going to the fuel pump soaked really bad, so I sprayed them with wires and connector cleaner and brake cleaner (i know bad idea). Then I used the connector cleaner again and i put everything back together and road tested the car and it's back to normal so far again. My son didn't know she had coffee made in the suit case. But I cleaned the throttle body and I didn't open the throttle plate just cleaned around it and now it had a code p0507 idle air control system rpm higher than expected so I will check it out tomorrow. With the ac on and you hit the gas pedal the rpm goes high and it stays high until I turn the ac off and I was in park i didn't notice it while I was driving. So I don't know if I have to relearn the throttle body, I guess I will find out later today. So cross my fingers lol .
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