DTC P0641. Isuzu Ascender

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2006 🢒 Ascender - 2WD 🢒 Engine 🢒 Engine Controls - 5.3L 🢒 DTC P0641

Circuit Description

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

•	The fuel tank pressure (FTP) sensor

•	The engine oil pressure (EOP) sensor

•	The manifold absolute pressure (MAP) sensor

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

•	The accelerator pedal position (APP) sensor 2

•	The brake booster vacuum sensor, RPO LH6 only

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 affect the other sensor 5-volt reference circuits. 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0641 5-Volt Reference 1 Circuit

Conditions for Running the DTC

•	DTCs P0601, P0602, P0603, P0604, P0606, P0607, P1621, P2610 are not set.

•	The ignition is ON.

•	The ignition voltage is more than 5.23 volts.

•	DTC P0641 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects a voltage out of tolerance condition on the 5-volt reference circuit for more than 0.5 second.

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 refers to the step number on the diagnostic table.

A short to voltage on the signal circuit of the MAP and FTP sensors may backfeed through the sensor into the 5-volt reference circuit and set this DTC.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	--	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Observe the Freeze Frame/Failure Records 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 Testing for Intermittent Conditions and Poor Connections
3	Turn OFF the ignition. Disconnect the engine oil pressure (EOP) sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the 5-volt reference circuit of the EOP sensor to a good ground with a DMM. Refer to Circuit Testing . Is the voltage within the specified range?	4.8-5.2 V	Go to Step 4	Go to Step 5
4	Connect the EOP 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 . Is the voltage within the specified range?	4.8-5.2 V	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 10
5	Is the voltage measured in step 3 more than the specified value?	5.2 V	Go to Step 8	Go to Step 6
6	Monitor the DMM while disconnecting all other sensors connected to this 5-volt reference bus, one at a time. Replace the component if the voltage returns to within the specified range when one of the above components is disconnected. Refer to the appropriate replacement procedure. Was a component replaced?	4.8-5.2 V	Go to Step 12	Go to Step 7
7	Test the 5-volt reference circuits of all the sensors connected to this 5-volt reference bus for a short to ground or any sensor low reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 12	Go to Step 11
8	Important: If a short to voltage occurs, the A/C refrigerant pressure sensor may be damaged. Test the 5-volt reference circuits of all the sensors connected to this 5-volt reference bus for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 12	Go to Step 9
9	Important: If a short to voltage occurs on the MAP sensor signal circuit or fuel tank pressure (FTP) sensor signal circuit, the sensors may be damaged. Test the MAP sensor signal circuit and FTP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 12	Go to Step 11
10	Replace the EOP sensor. Refer to Engine Oil Pressure Sensor and/or Switch Replacement . Did you complete the replacement?	--	Go to Step 12	--
11	Replace the engine control module (ECM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	--	Go to Step 12	--
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
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 - Vehicle	System OK