Circuit Description
The fuel rail temperature (FRT) sensor is a variable resistor that measures the temperature of the fuel in the compressed natural gas (CNG) fuel rail. The fuel injector control module (FICM) supplies 5 volts to the FRT signal circuit and supplies a ground to the low reference circuit. The FICM monitors the FRT sensor voltage and communicates the data to the powertrain control module (PCM) by a dedicated pulse width modulated (PWM) circuit. This DTC sets when the FRT temperature is not near the expected temperature.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0186 Fuel Rail Temperature Sensor Performance
Conditions for Running the DTC
| • | The ignition is ON after the engine has been OFF for 10 hours. |
| • | The intake air temperature (IAT) and engine coolant temperature (ECT) are the same. |
Conditions for Setting the DTC
The FRT sensor is not at the expected temperature.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic 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 Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | 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 IAT values should display within a few degrees. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
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 |
Important: Other DTCs may set. Does the scan tool indicate that the FRT is more than the specified value? | 4.95 V | Go to Step 3 | Go to Step 7 |
3 |
Does the scan tool indicate that the FRT is the same or less than the specified value? | 0.02 V | Go to Step 8 | Go to Step 4 |
4 |
Does the scan tool indicate that the FRT is the same or less than the specified value? | 0.02 V | Go to Step 6 | Go to Step 5 |
5 | Test the signal circuit of the fuel tank temperature (FTT) 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 12 | Go to Step 9 |
6 | Test the low reference circuit of the FTT 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 12 | Go to Step 9 | |
7 | Test the signal circuit of the FTT sensor for a shorted to ground condition. 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 12 | Go to Step 9 |
8 | Test for an intermittent and for a poor connection at the FTT 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 12 | Go to Step 10 |
9 | Test for an intermittent and for a poor connection at the fuel injector control module (FICM). 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 12 | Go to Step 11 |
10 | Replace the FRT sensor. Refer to Fuel Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
