Diagnostic Instructions
DTC Descriptors
DTC P0087: Fuel Rail Pressure (FRP) Too Low
DTC P0088: Fuel Rail Pressure (FRP) Too High
DTC P0089: Fuel Pressure Regulator Performance
Circuit/System Description
The fuel rail pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5-volt reference voltage on the 5-volt reference circuit and ground on the low reference circuit. The ECM receives a varying
signal voltage on the signal circuit.
High pressure fuel is regulated by the fuel rail pressure (FRP) regulator, which is a part of the high pressure fuel pump. The FRP regulator is a solenoid valve. The ECM provides battery voltage on the FRP regulator high circuit and ground on the FRP regulator
low circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the FRP regulator low circuit driver connects the low circuit to ground and the FRP regulator high circuit driver pulse-width
modulates (PWM) the high circuit.
The high pressure mechanical fuel pump is driven by three lobes on the camshaft. The ECM uses the camshaft and crankshaft position sensor inputs to synchronize the FRP regulator with the position of each of these camshaft lobes. The ECM regulates fuel
pressure by adjusting the portion of each pump stroke that provides fuel to the rail.
The ECM creates a feedback loop between the pressure sensor and the FRP regulator. If the difference between expected and actual inputs exceeds a calibrated value, or if the amount of correction exceeds a calibrated value, a DTC sets.
Conditions for Running the DTC
| • | DTCs P0090, P0091, P0092, P0192, P0193 are not set. |
| • | The ignition 1 signal parameter is less than 18.1 volts. |
| • | The relative injected fuel mass is between 5.016-500 percent. |
| • | The deceleration fuel cut-off (DFCO) is inactive. |
| • | The engine speed is greater than 25 RPM. |
| • | The engine start temperature is greater than -48°C (-54.4°F) |
| • | The DTCs run continuously when the above conditions are met for 2 seconds. |
Conditions for Setting the DTC
P0087
The actual fuel pressure is 1500 kPa (218 psi) less than the desired fuel pressure.
P0088
The actual fuel pressure is 2000 kPa (290 psi) greater than the desired fuel pressure.
P0089
| • | The fuel pressure adjustment is greater than +2,500 kPa (+363 psi) or less than -2,500 kPa (-363 psi). |
| • | The DTCs set when the above conditions are met for 5 seconds. |
Action Taken When the DTC Sets
| • | DTCs P0087, P0088, and P0089 are Type B DTCs. |
| • | A message center or an indicator displays Reduced Engine Power when DTC P0087 sets. |
Conditions for Clearing the DTC
DTCs P0087, P0088, and P0089 are Type B DTCs.
Diagnostic Aids
| • | A skewed fuel rail pressure (FRP) sensor may set these DTCs. |
| • | Faulty fuel injectors may set DTCs P0087 or P0089. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Fuel System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- If any other DTCs are set, perform those diagnostics first.
- Operate the vehicle within the parameters described in Conditions for Running and Conditions for Setting. The DTC should not set this ignition.
| ⇒ | If the DTC sets this ignition, proceed with Circuit/System Testing. |
Circuit/System Testing
Note: Circuit/System Verification must be performed first or misdiagnosis may result.
- Verify the correct low side fuel system pressure. Refer to
Fuel System Diagnosis.
- Remove the G18 high pressure fuel pump and visually inspect the lobes on the camshaft for wear.
| ⇒ | If the lobes are normal, replace the G18 high pressure fuel pump. |
| ⇒ | If the lobes are worn, replace the camshaft. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
