DTC P2066 or P2636. Cadillac XLR 2006

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2006 🢒 XLR 🢒 DTC 🢒 DTC P2066 or P2636

Circuit Description

The primary (left) fuel level sender and the secondary (right) fuel level sender change resistance in response to fuel level. The engine control module (ECM) monitors the signal circuit of the primary fuel level sender and the signal circuit of the secondary fuel level sender in order to determine the fuel level. When the fuel tanks are full, the resistances of both fuel level senders are high, and the ECM senses a high signal voltage on both the signal circuit of the primary fuel level sender and the signal circuit of the secondary fuel level sender. When the fuel tanks are empty, the resistances of the fuel level senders are low, and the ECM senses a low signal voltage. The ECM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of remaining fuel in the tanks. The ECM sends the fuel level percentage via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

This diagnostic tests for a stuck secondary (right) fuel level sensor signal. The ECM sets this DTC if the secondary fuel level sensor signal appears to be stuck based on a lack of signal variation expected during normal operation.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

•	DTC P2066 Fuel Level Sensor 2 Performance

•	DTC P2636 Fuel Transfer Pump Flow Insuffient

Conditions for Running the DTC

DTC P2066

•	The engine is running.

•	Fuel level is greater than 32 L (8.45 gal)

•	No VSS DTCs set.

DTC P2636

•	The engine is running.

•	DTC P2636 runs contonuosly once the conditions have been met

Conditions for Setting the DTC

P2066

•	The ECM does not detect a change in the secondary (right) fuel level of at least 3 L (0.79 gal) over a distance of 200 km (124 mi).

•	The ECM detects that the primary (left) fuel tank is less than 28 L (7.3 gal) and the secondary (right) fuel tank is more than 4 L (1 gal) and the condition is present for 30 minutes.

•	The ECM detects that the primary (left) fuel tank is greater than 28 L (7.3 gal) and the secondary (right) fuel tank is less than 4 L (1 gal) over a distance of 200 km (124 mi).

P2636

The ECM detects that the primary (left) fuel tank is less than 28 L (7.3 gal) and the secondary (right) fuel tank is more than 4 L (1 gal) and the condition is present for 30 minutes.

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 the clear code command from the scan tool.

Diagnostic Aids

Use the Freeze Frame/Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data may help in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also help in determining the number of ignition cycles that the diagnostic test reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions, including those for RPM, for engine load, for vehicle speed, for temperature, and for others. This will isolate at what point the DTC failed.

Refer to Testing for Intermittent Conditions and Poor Connections .

Step

Action

Yes

Schematic Reference: Instrument Cluster Schematics

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

Remove the secondary (right) fuel tank module.
Inspect for the following items:

•	The fuel level sensor is stuck, perhaps due to an interference with the fuel strainer.

•	The fuel tank contains foreign material, for instance, ice.

•	A clogged or restricted siphon jet pump.

•	Broken, clogged or restricted flex tubes.

•	Broken, clogged, disconnected or restricted fuel transfer tube inside tank.

Did you find and correct the condition?

Go to Step 4

Go to Step 3

Replace the secondary (right) fuel tank module. Refer to Fuel Tank Fuel Pump Module Replacement - Right Side for the 4.6 L engine or Fuel Tank Fuel Pump Module Replacement - Right Side for the 4.4 L engine.

Did you complete the replacement?

Go to Step 4

Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK