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Pinpoint Test K: The Check Fuel Cap Indicator Is Never/Always On

Normal Operation 

The PCM monitors the fuel tank evaporative emission system for significant leaks that occur following refueling of the vehicle. Once the PCM detects a fuel vapor leak, the PCM sends the instrument cluster (IC) a message over the communication network to turn on the check fuel cap indicator. DTC P0457 sets in the PCM following a successful cruise test, which is initiated when the vehicle is driven at a steady speed above 64 km/h (40 mph) for a duration of approximately 4-5 minutes. If the PCM is unable to successfully run the cruise test, the instrument cluster (IC) does not receive the check fuel cap message and the check fuel cap indicator remains off.

If the instrument cluster (IC) does not receive the fuel cap off data from the PCM for 5 seconds or less, the instrument cluster (IC) defaults the check fuel cap indicator to the last setting, based upon the last known good data message. If the instrument cluster (IC) does not receive the fuel cap off data from the PCM for more than 5 seconds or if the data received is deemed invalid, the instrument cluster (IC) sets DTC U0100 in continuous memory and defaults the fuel cap off indicator off.

NOTE: If DTC U0100 is set in the instrument cluster (IC), other observable symptoms may be an inoperative speedometer, temperature gauge or odometer.

The PCM sets DTC P0457 if a fuel tank pressure change greater than -23.7 kPa (-7 in-Hg) of vacuum within 30 seconds after refueling occurs, or there is an excessive purge (fuel vapor) flow of greater than 454 g (1.0 lb) per minute.

This pinpoint test is intended to diagnose the following:

PINPOINT TEST K: THE CHECK FUEL CAP INDICATOR IS NEVER/ALWAYS ON 

  1. K1 CARRY OUT THE INSTRUMENT CLUSTER (IC) INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL 
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: Instrument Cluster (IC) DataLogger
    • Select the instrument cluster (IC) fuel gauge (FUEL_CAP) active command and command the check fuel cap indicator on and off. Observe the check fuel cap indicator.
    • Does the check fuel cap indicator illuminate when commanded on, and turn off when commanded off? 
    1. YES  : Go to  K2.
    2. NO  : Go to  K5.
  2. K2 RETRIEVE THE RECORDED DTCs FROM BOTH CONTINUOUS AND ON-DEMAND PCM SELF-TESTS 
    • Check for recorded PCM DTCs from the continuous and on-demand self-tests.
    • Is DTC P0457 recorded? 
    1. YES  : If the check fuel cap indicator is illuminated, REFER to the Introduction - Gasoline Engines article.

      If the check fuel cap indicator is not illuminated, go to  K3.

    2. NO  : If the check fuel cap indicator is always on, go to  K5.

      If the check fuel cap indicator is not illuminated, the system is operating normally at this time. If the fuel cap was left off and the check fuel cap warning indicator did not turn on, driving conditions may not have allowed for the PCM to run the cruise test and message the instrument cluster (IC) to turn on the check fuel cap warning indicator.

  3. K3 RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND INSTRUMENT CLUSTER (IC) SELF-TESTS 
    • Check for recorded instrument cluster (IC) DTCs from the continuous and on-demand self-tests.
    • Is DTC U0100 recorded? 
    1. YES  : Go to Pinpoint Test AG  .
    2. NO  : Go to  K4.
  4. K4 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the PCM connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS article. TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
  5. K5 CHECK FOR CORRECT INSTRUMENT CLUSTER (IC) OPERATION 
    • Disconnect the instrument cluster (IC) connector.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect the instrument cluster (IC) connector and make sure it seats correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new instrument cluster (IC). REFER to Instrument Cluster (IC) . TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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