GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 C-Series Medium Duty Truck C6/7/8 - Mexico 🢒 DTC 🢒 DTC P0523

Circuit Description

The engine oil pressure (EOP) sensor changes resistance based on engine oil pressure. The powertrain control module (PCM) monitors the signal circuit of the EOP sensor. When the engine oil pressure is high, the sensor resistance is high and the PCM senses a high signal voltage. When the engine oil pressure is low, the sensor resistance is low and the PCM senses a low signal voltage. The PCM sends the engine oil pressure information to the instrument panel cluster (IPC) via the class 2 serial data circuit.

Conditions for Running the DTC
    • The ignition is ON.
    • DTC P1635 (LB7, LLY and late L18) is present.

Conditions for Setting the DTC
    • The PCM detects that the EOP sensor signal circuit is greater than 4.6 volts.
    • The above condition is present for greater than 9 seconds.

Action Taken When the DTC Sets

The PCM records the operating conditions at the time that the diagnostic test fails. The PCM displays this information in the Failure Records on the scan tool.

Conditions for Clearing the DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC is cleared after 40 malfunction-free warm-up cycles.
    • The PCM receives the clear code command from the scan tool.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help in determining how many miles since the DTC set. The Fail Counter and the Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests for the proper operation of the circuit in the low voltage range.

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With the scan tool, observe one of the following engine oil pressure parameters:
    4. • Monitored Oil Pressure parameter in the IPC data list (LB7, LLY and LG4 only).
    • Engine Oil Pressure Sensor parameter in the PCM Engine Data 2 data list (L18 only).

Does the scan tool indicate that the engine oil pressure parameter is at or greater than the specified value?

550 kPa (80 psi)-LB7, LLY and LG4 only

4.6 V-L18 only

Go to Step 3

Go to Diagnostic Aids

3

Is DTC P1635 (LB7, LLY and late L18) current in the powertrain control module (PCM)?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 8.1L

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Disconnect the engine oil pressure (EOP) sensor.
  3. With the scan tool, observe one of the following engine oil pressure parameters:
    4. • Monitored Oil Pressure parameter in the IPC data list (LB7, LLY and LG4 only).
    • Engine Oil Pressure Sensor parameter in the PCM Engine Data 2 data list (L18 only).

Does the scan tool indicate that the engine oil pressure parameter is at or less than the specified value?

0 kPa (0 psi)-LB7, LLY and LG4 only

0.4 V-L18 only

Go to Step 5

Go to Step 6

5
  1. Turn the ignition OFF.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. Measure the resistance from the low reference circuit of the EOP sensor to a good ground.

Is the resistance less than the specified value?

5 ohms

Go to Step 8

Go to Step 7

6

Test the EOP sensor signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

7
  1. Disconnect the PCM.
  2. Test the low reference circuit of the EOP sensor for an open or for a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the EOP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

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 in Engine Mechanical - 8.1L.

Did you complete the replacement?

--

Go to Step 12

--

11

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

--

Go to Step 2

System OK