For 1990-2009 cars

### 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 P0194 00: Fuel Rail Pressure Sensor Circuit Erratic

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0651 00 | P0192 5A, P0192 12 | P0651 00 | --
Signal | P0192 5A, P0192 12 | P0192 5A, P0192 12 | P0193 11, P0193 5B | P0194 00
Low Reference | P0192 5A, P0192 12 | P0192 5A, P0192 12 | -- | --

### Typical Scan Tool Data

#### Fuel Rail Pressure Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: engine running Parameter Normal Range: 0.5-4.8 V
5-Volt Reference | 5 V | 5 V | --
Signal | 0 V | 5 V | 5 V
Low Reference | -- | 5 V | --

### Circuit/System Description

The fuel rail pressure sensor measures the fuel pressure within the fuel rail. The engine control module (ECM) monitors the voltage on the fuel rail pressure sensor circuits. When the fuel pressure is low, the signal voltage is low. When the fuel pressure is high, the signal voltage is high. The ECM supplies 5 V to the 5-volt reference circuit and a ground to the low reference circuit. The fuel rail pressure sensor provides a signal voltage to the ECM, relative to the pressure changes within the fuel rail, on the fuel rail pressure sensor signal circuit.

### Conditions for Running the DTC

• | The engine is running.

• | The DTCs run continuously when the above conditions are met.

### Conditions for Setting the DTC

The ECM detects that the fuel pressure sensor signal is not plausible.

### Action Taken When the DTC Sets

DTCs P0194 is a Type C DTC.

### Conditions for Clearing the DTC

DTCs P0194 is a Type C DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Fuel System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

1. Ignition On, observe the DTC information with a scan tool. Verify that DTC P0192 or P0193 is not set.

⇒ | If the DTC is set, refer to DTC P0192 or P0193

2. Observe the scan tool Fuel Rail Pressure Sensor voltage parameter. The reading should be between 0.5 and 4.5 V.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Perform the Fuel System Diagnosis
2. Ignition OFF, disconnect the harness connector at the B47 Fuel Pressure Sensor.
3. Test for less than 5 Ω between the low reference circuit terminal 1 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 K20 Engine Control Module (ECM).

4. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 3 and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.3 V.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

7. If all circuits test normal, replace the B47B Fuel Rail Pressure (FRP) Sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification

• | Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

• | Control Module References