P2636

DTC P2066 or P2636

DTC Descriptor

DTC P2066
- Fuel Level Sensor 2 Circuit Performance

DTC P2636
- Fuel Transfer Pump Flow Insufficient

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit/System Description

The secondary (right) fuel level sender changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the secondary (right) fuel level sender in order to determine the fuel level. When the fuel tank is full, the secondary (right) fuel level sender resistance is high and the ECM senses a high signal voltage. When the fuel tank is empty, the secondary (right) fuel level sender resistance is low and the ECM senses a low signal voltage. The ECM uses the signal circuit of the secondary (right) fuel level sender in order to calculate the percentage of remaining fuel in the secondary tank. The ECM sends the fuel level information via GMLAN serial data circuit to the instrument panel cluster (IPC) for display in the fuel gage. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.

Conditions for Running the DTC

P2066
* The engine is running.
* The fuel level is greater than 32 L (8.45 gals)
* No VSS DTCs set

P2636
* The engine is running.
* DTC P2636 runs continuously once the conditions have been met

Conditions for Setting the DTC

P2066

The ECM does not detect a change in fuel level in the secondary (right) fuel tank of at least 3 L (0.79 gals) over a distance of 320 km (200 miles).

P2636
* The ECM detects that the primary (left) fuel tank is less than 6.25 L (1.7 gal) and the secondary (right) fuel tank is more than 33 L (8.7 gal).
* The above condition is present for 1 minute.

Action Taken When the DTC Sets

* The fuel gage defaults to empty.
* The malfunction indicator lamp (MIL) will not illuminate.
* The driver information center (DIC) displays the FUEL LEVEL LOW message.
* The ECM records the operating conditions at the time that the diagnostic test fails. The ECM displays the failure 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 clears after 40 malfunction-free warm-up cycles.
* The ECM receives a clear code command from the scan tool.

Circuit/System Testing

1. Ignition OFF, remove the secondary (right) fuel level sender and verify there are no objects interfering with the fuel level sender.

• Repair any fuel level sender interference.

2. Replace the secondary (right) fuel level sender.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Fuel Tank Module Replacement - Right Side for the 6.0L engine
* Fuel Tank Module Replacement - Right Side for the 7.0L engine
* Refer to Programming and Relearning.Programming and Relearning