Chevrolet Silverado / GMC Sierra. Service manual — part 2425

Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.

2. Ignition OFF, test for less than 1 ohm between the fuel level sensor low reference circuit

terminal B and ground.

If greater than the specified range, test the low reference circuit for an open/high
resistance. If the circuit tests normal, replace the ECM.

3. Install a Signal Generator and Instrument Panel Tester between the fuel level sensor signal

circuit terminal C and the fuel level sensor low reference circuit terminal B.

4. Ignition ON, vary the signal generator resistance between 40 and 250 ohms. Verify that the

scan tool Fuel Tank Level Remaining parameter displays a range that varies between 5 and
95 percent as the signal generator resistance changes.

If not within the specified range, test the signal circuit for an open/high resistance. If
the circuit test normal, replace the ECM.

5. If all circuits test normal, perform the fuel level sensor component test before replacing the

fuel level sensor.

Component Testing

1. Ignition OFF, disconnect the harness connectors at the fuel level sensor.

2. While sweeping the fuel level sensor through its full range of motion, test for a minimum

value less than 41 ohms and a maximum value greater than 119 ohms of resistance between
the signal terminal C and the low reference terminal B.

If not within the specified range, replace the fuel level sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Level Sensor Replacement (Extended Cab w/26 Gal Tank) or Fuel Level Sensor
Replacement (Regular Cab w/34 Gal Tank) or Fuel Level Sensor Replacement
(Regular Cab w/26 Gal Tank) for the 4.3L engine

Fuel Level Sensor Replacement (15 Reg Cab w/26 gal Tank) or Fuel Level Sensor

2008 Chevrolet Silverado 1500

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Replacement (15 Ext/Crew Cab w/26 gal Tank) or Fuel Level Sensor Replacement
(25 Ext/Crew Cab w/26 gal Tank) or Fuel Level Sensor Replacement (15/25
Reg/Ext/Crew Cab w/34 gal Tank) or Fuel Level Sensor Replacement (35
Reg/Ext/Crew Cab w/34 gal Tank) for the 4.8L, 5.3L, 6.0L, and 6.2L engines

Fuel Level Sensor Replacement (Cab/Chassis - Rear Tank) for the 6.6L engine

Control Module References for the ECM replacement, setup, and programming

DTC P0521, P0522, OR P0523

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 P0521

Engine Oil Pressure (EOP) Sensor Performance

DTC P0522

Engine Oil Pressure (EOP) Sensor Circuit Low Voltage.

DTC P0523

Engine Oil Pressure (EOP) Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Engine Oil
Pressure 5-
Volt Reference

P0522

1

P0522

P0523

P0521

Engine Oil
Pressure
Sensor Signal

P0522

1

P0522

P0523

P0521

Low Reference

-

1

P0523

-

P0521

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

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Circuit/System Description

The engine oil pressure (EOP) sensor changes voltage based on the engine oil pressure. The EOP
sensor is a 3-wire sensor comprising of the signal circuit, the low reference circuit and the 5-volt
reference circuit. The engine control module (ECM) supplies 5 volts to the EOP sensor via the 5-
volt reference circuit and provides ground via the EOP low reference circuit. The ECM monitors
the signal circuit of the EOP sensor to determine the EOP sensor voltage is within the normal
operating range of approximately 1-4 volts. When the engine oil pressure is high, the EOP sensor
voltage is high and the ECM senses a high signal voltage. When the engine oil pressure is low, the
EOP sensor voltage is low and the ECM senses a low signal voltage. The ECM sends the EOP
information to the instrument panel cluster (IPC) via GMLAN serial data message.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P0521

The ECM detects that the difference between the predicted oil pressure and the actual oil
pressure is either less than 47 kPa (6.8 psi) or greater than 50 kPa (7.3 psi).

P0522

The ECM detects that the EOP sensor signal circuit is less than 0.1 volt.

The above condition is present for greater than 10 seconds.

P0523

The ECM detects that the EOP sensor signal circuit is greater than 4.4 volts.

The above condition is present for greater than 10 seconds.

Action Taken When the DTC Sets

The ECM records the operating conditions at the time the diagnostics test fails. The ECM
displays this information in the Failure Records on the scan tool.

The IPC illuminates the EOP indicator.

Conditions for Clearing the DTC

1. Engine Oil Pressure Indicator Malfunction

2008 Chevrolet Silverado 1500

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The DTC becomes history when the conditions for setting the DTC are no longer present.

The history DTC clears after 40 malfunction-free warm-up cycles.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Instrument Cluster Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Engine running, observe the scan tool Engine Oil Pressure Sensor parameter. The reading

should be between 41-448 kPa (6-65 psi).

2. Verify the engine oil pressure, refer to Oil Pressure Diagnosis and Testing .

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) sensor.

2. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal 1 and

ground.

If greater than the specified range, test the low reference circuit for an open/high

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado