Circuit Description
The fuel rail temperature (FRT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel rail. The alternative fuels ECM supplies 5 volts to the FRT signal circuit and supplies a ground to the low reference circuit. This DTC sets when the FRT signal voltage is above the normal operating range of the sensor.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The intake air temperature is more than -10°C (14°F). |
| • | DTCs P0112, and P0113 are not set. |
Conditions for Setting the DTC
The alternative fuels ECM detects that the fuel rail temperature sensor voltage is more than 4.95 V for more than 5 seconds.
Action Taken When the DTC Sets
The Alternative Fuels ECM records the operating conditions at the time the diagnostic fails. The Alternative Fuels ECM stores this information in the Freeze Frame and/or Failure Records.
Conditions for Clearing the MIL/DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
| • | If a short to a separate 5-volt source occurs this DTC may set, if this is found to be the condition a continuity test to all other PCM circuits will be necessary to diagnose the specific circuit. |
| • | Use the Temperature vs Resistance table in order to test the FRT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FRT sensor and the intake air temperature values should display within a few degrees. If the temperatures are not within 3°C (5°F), refer to Fuel Rail Temperature Sensor Output Voltage Versus Temperature Resistance . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
-
This step tests the signal circuit of the FRT sensor for a short to another 5.0 volt reference circuit.
Step | Action | Values | 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) | ||||
2 |
Does the scan tool indicate that the FRT is at the specified value? | 5 V | Go to Step 4 | Go to Step 3 | ||||
3 |
Does the DTC fail this ignition cycle? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||
Does the scan tool indicate that the FRT is at the specified value? | 0 V | Go to Step 8 | Go to Step 5 | |||||
5 |
Does the scan tool indicate that the FRT is at the specified value? | 0 V | Go to Step 7 | Go to Step 6 | ||||
6 | Test the signal circuit of the FRT sensor for an open circuit or for high resistance. 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 14 | Go to Step 10 | ||||
7 | Test the low reference circuit of the FRT sensor for a high resistance 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 14 | Go to Step 10 | ||||
Important: If the fuse in the jumper wire opens, repair the short to B+, and replace the sensor. Refer to Fuel Temperature Sensor Replacement . Do any additional DTCs set? | -- | Go to Step 11 | Go to Step 9 | |||||
9 | Test for an intermittent and for a poor connection at the FRT sensor. 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 14 | Go to Step 12 | ||||
10 | Test for an intermittent and for a poor connection at 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 14 | Go to Step 13 | ||||
11 | Repair the short between the signal circuit of the FRT sensor and the circuit for which the DTC set. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you complete the repair? | -- | Go to Step 14 | -- | ||||
12 | Replace the FRT sensor. Refer to Fuel Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
13 | Replace the alternative fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 | ||||
15 | 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 | |||||
