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Chevrolet Silverado / GMC Sierra. 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
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 &
Silverado
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
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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
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