For 1990-2009 cars

## DTC P2066 3.6L (LY7)

### 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 Descriptor

DTC P2066: Fuel Level Sensor 2 Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fuel Level Sensor Reference Voltage Circuit | P2067 | -- | -- | P2066
Fuel Level Sensor Signal Secondary Circuit | P2067 | P2068¹ | P2068 | P2066
Fuel Level Sensor Low Reference Circuit | -- | P2068¹ | P2068 | P2066
¹Fuel Gage Inaccurate or Inoperative

### Circuit/System Description

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

### Conditions for Running the DTC

• | The vehicle speed sensor DTC is not set.

• | No electronic fuel level sensor failure is present.

• | The ignition 1 voltage is between 10.5-18 volts.

• | The engine is running.

• | The fuel level state is stable.

• | The vehicle speed is greater than 0 km/h (0 mph).

• | The inspection is done more than once.

• | The difference between the engine consumed fuel and change of the fuel level signal is greater than 45.6 percent or less than -45.6 percent.

| OR

• | The primary fuel level is less than 29.4 percent.

• | The secondary fuel level is less than or equal to 10.3 percent.

• | Supply voltage is between 10.5-18 volts.

• | Keep the engine running.

• | The electrical fuel level sensor is not faulty.

• | The DTC P2066 runs continuously once the above condition is present.

### Conditions for Setting the DTC

• | The fuel level sensor signal offset is less than the specified value.

• | The accumulated distance travelled is more than the specified millage.

• | The above condition is present for about 4 seconds.

### Action Taken When the DTC Sets

• | The fuel gage defaults to empty.

• | The driver information center (DIC) displays the FUEL LEVEL LOW message.

• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnosis runs and fails.

• | The control module records the operating conditions at the time of the failure. The first time the diagnosis fails, the control module stores this information in the Failure Records. If the diagnosis reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure.

### 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.

### Reference Information

#### Fuel Level Specifications

Fuel Level Specifications

#### Schematic Reference

• | Instrument Cluster Schematics

• | Engine Controls Schematics

#### Connector End View Reference

• | Component Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Testing

1. Ignition OFF, remove the secondary fuel level sensor and check if the fuel tank level sensor is stuck.

⇒ | If there is anything stuck, remove the obstruction.

2. If there is nothing stuck, replace the secondary fuel level sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Secondary Fuel Tank Module Replacement

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

## DTC P2066 4.6L (LH2)

### 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 Descriptor

DTC P2066: Fuel Level Sensor 2 Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fuel Level Sensor Reference Voltage Circuit | P2067 | -- | -- | P2066
Fuel Level Sensor Signal Secondary Circuit | P2067 | P2068¹ | P2068 | P2066
Fuel Level Sensor Low Reference Circuit | -- | P2068¹ | P2068 | P2066
¹Fuel Gage Inaccurate or Inoperative

### Circuit/System Description

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

### Conditions for Running the DTC

• | The vehicle speed sensor DTC is not set.

• | Engine is running.

• | The DTC P0641 runs continuously once the above condition is present.

### Conditions for Setting the DTC

The ECM detects a change in fuel level in the primary fuel tank of less than 3.0L over a distance of 100 km.

### Action Taken When the DTC Sets

• | The fuel gage defaults to empty.

• | The driver information center (DIC) displays the FUEL LEVEL LOW message.

• | DTC P2066 is a type B DTC.

### Conditions for Clearing the DTC

DTC P2066 is a type B DTC.

### Reference Information

#### Fuel Level Specifications

Fuel Level Specifications

#### Schematic Reference

• | Instrument Cluster Schematics

• | Engine Controls Schematics

#### Connector End View Reference

• | Component Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Testing

1. Ignition OFF, remove the secondary fuel level sensor and check if the fuel tank level sensor is stuck.

⇒ | If there is anything stuck, remove the obstruction.

2. If there is nothing stuck, replace the secondary fuel level sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Secondary Fuel Tank Module Replacement

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