DTC P0641. Saturn ION 2003

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2003 🢒 ION 🢒 Engine 🢒 Engine Controls - 2.2L (L61) 🢒 DTC P0641

Circuit Description

The engine control module (ECM) provides 5 volts to the following sensors:

•	The intake air temperature (IAT) sensor

•	The manifold absolute pressure (MAP) sensor

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

•	The fuel tank pressure (FTP) sensor

•	The engine coolant temperature (ECT) sensor

•	The throttle position (TP) sensor

•	The fuel level sender

These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore a circuit condition on one sensor 5-volt reference circuit may adversely affect the other sensor 5-volt reference circuits. This condition may result in diagnostic trouble codes (DTCs) for any or all of these sensors. The ECM monitors the voltage on the 5-volt reference circuit, if the ECM detects that the voltage is out of tolerance, DTC P0641 sets.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The ECM detects a voltage out of tolerance condition on the 5-volt reference circuit.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Test Description

The number below refer to the number on the diagnostic table.

This step will determine if the TP sensor is responsible for a fault.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Observe the Freeze Frame/Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

Turn OFF the ignition.
Disconnect the throttle position (TP) sensor.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the 5-volt reference circuit of the TP sensor, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 5

Go to Step 4

Is the voltage measured in the previous step more than the specified value?

5.2 V

Go to Step 8

Go to Step 6

Connect the TP sensor.
Disconnect the manifold absolute pressure (MAP) sensor.
Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is voltage within the specified range?

4.8-5.2 V

Go to Intermittent Conditions

Go to Step 10

Monitor the DMM while disconnecting all other devices connected to 5-volt reference circuit, one at a time. Refer to Engine Controls Component Views .
If the voltage changes when one of the devices are disconnected, replace the component. Refer to the appropriate replacement procedure below:

•	The MAP sensor--Refer to Manifold Absolute Pressure Sensor Replacement .

•	The engine coolant temperature (ECT) sensor--Refer to Engine Coolant Temperature Sensor Replacement .

•	The intake air temperature (IAT) sensor--Refer to Intake Air Temperature Sensor Replacement .

•	The fuel tank pressure (FTP) sensor--Refer to Fuel Tank Pressure Sensor Replacement .

•	The air conditioning (A/C) pressure sensor--Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC.

•	The fuel level sender--Refer to Fuel Level Sensor Replacement .

Was a component replaced?

Go to Step 12

Go to Step 7

Test the 5-volt reference circuit for a short to ground or any sensor low reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

Monitor the DMM while disconnecting the MAP sensor and the FTP sensor, one at a time. Refer to Engine Controls Component Views .
If the voltage returns to within the specified value when one of the devices are disconnected, test that sensors signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

4.8-5.2 V

Go to Step 12

Go to Step 9

Test the 5-volt reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

Replace the TP sensor. Refer to Throttle Position Sensor Replacement .

Did you complete the replacement?

Go to Step 12

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 12

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 13

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK