Circuit Description
The fuel rail pressure (FRP) sensor is a pressure sensor. The alternative fuels engine control module (ECM) supplies about 5 volts on the FRP sensor reference voltage circuit. The alternative fuels ECM also supplies a ground circuit to the FRP sensor. When the fuel rail pressure is normal, the FRP signal voltage rises to near 2.5 volts. If the fuel rail pressure increases, the MAP signal voltage increases. The alternative fuels ECM monitors the FRP signal circuit voltage in order to determine the correct fuel injector pulse width modulation.
This DTC sets when the FRP sensor signal voltage is more than the normal operating range of the sensor.
Conditions for Running the DTC
| • | The engine speed is greater than 100 RPM. |
| • | alternative fuels ECM DTC P0336 is not set. |
Conditions for Setting the DTC
The alternative fuels ECM monitors a FRP sensor signal voltage of more than 4.95 volts for at least 10 seconds continuously.
Action Taken When the DTC Sets
| • | A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History. |
| • | The Alternative Fuels ECM will illuminate the MIL and store the DTC as History after 2 consecutive drive trips that the diagnostic runs and fails. |
| • | The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | The Last Test Failed status will clear when the DTC runs and passes. |
| • | The Alternative Fuels ECM will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes. |
| • | The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC. |
| • | All DTC Information can be cleared with a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the condition is present.
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This step determines if an open sensor ground circuit condition is present. The FRP, FRT, FTP and FTT share a sensor ground. An open circuit between the splice and the alternative fuels ECM will cause all signal circuits to indicate high voltage.
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This step determines if an open or shorted signal circuit is the cause of the condition.
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This step determines if a shorted 5-volt reference circuit is the cause of the condition.
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This step determines if an open sensor ground circuit between the harness connector of the FRP sensor and the splice is the cause of the condition.
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The Fuel System Diagnosis procedure will determine if incorrect fuel pressure or the FRP sensor is the cause of the condition.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Alternative Fuels (Engine Controls) | ||||
Does the scan tool display the FRP sensor voltage more than the specified value? | 4.95 V | Go to Step 4 | Go to Step 3 | |||||
3 |
Does the DTC fail this ignition cycle? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||
Observe the fuel rail temperature (FRT) sensor data display with a scan tool. Does the scan tool display the FRT sensor voltage more than the specified value? | 4.7 V | Go to Step 8 | Go to Step 5 | |||||
Important: If the jumper fuse opens, repair the signal circuit short to battery voltage. Does the scan tool display the FRP sensor voltage less than the specified value? | 0.05 V | Go to Step 6 | Go to Step 9 | |||||
Does the DMM display a voltage more than the specified value? | 5.2 V | Go to Step 10 | Go to Step 7 | |||||
Probe the ground circuit of the FRP sensor with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 13 | |||||
8 | Test the ground circuit of the FRP sensor for an open between the alternative fuels ECM and the splice. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||
9 | Test the signal circuit of the FRP sensor for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||
10 | Test the 5-volt reference circuit of the FRP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | ||||
Inspect for proper terminal contact at the harness connector of the FRP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 15 | Go to Fuel System Diagnosis | |||||
12 | Inspect for proper terminal contact at the harness connector of the alternative fuels ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | ||||
13 | Repair the ground circuit of the FRP sensor for an open, or high resistance, between the harness connector of the FRP sensor and the splice. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you complete the repair? | -- | Go to Step 15 | -- | ||||
14 | Replace the alternative fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||
15 |
Does the DTC run and pass? | -- | Go to Step 16 | Go to Step 2 | ||||
16 | With a scan tool, select Capture Info in order to observe the stored information. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
