Pinpoint Test F: Inaccurate Tachometer Indication

Normal Operation 

The PCM uses the crankshaft position (CKP) sensor to measure the engine RPM, and sends the instrument cluster (IC) data over the high speed controller area network (HS-CAN) communication bus, to command the tachometer gauge according to the data.

If the instrument cluster (IC) does not receive the engine RPM data from the PCM for 5 seconds or less, the instrument cluster (IC) defaults the tachometer to the last setting, based upon the last known good RPM message. If the instrument cluster (IC) does not receive the engine RPM 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 tachometer to 0 RPM.

This pinpoint test is intended to diagnose the following:

• PCM
• Instrument cluster (IC)

PINPOINT TEST F: INACCURATE TACHOMETER INDICATION 

1. F1 RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND PCM SELF-TESTS 
   • Check for recorded PCM DTCs from the continuous and on-demand self-tests.
   • Are any PCM DTCs recorded? 
   1. YES  : REFER to the Introduction - Gasoline Engines article.
   2. NO  : Go to  F2.
2. F2 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  F3.
3. F3 OBSERVE THE TACHOMETER OPERATION 
   • Key in ON position.
   • With the engine running, observe the tachometer while increasing the engine speed between 0 and 2,000 RPM.
   • Key in OFF position.
   • Does the tachometer begin at 0 RPM, increase with engine RPM then return to 0 RPM with the engine off? 
   1. YES  : Go to  F4.
   2. NO  : Go to  F6.
4. F4 CARRY OUT THE INSTRUMENT CLUSTER (IC) TACHOMETER 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) tachometer (TACH) active command and command the tachometer in increments of 10%. Observe the tachometer. The tachometer should start at 0 and increase by approximately 700 RPM for each 10% increment.
   • Does the tachometer increase by approximately 700 RPM for each 10% increment? 
   1. YES  : Go to  F5.
   2. NO  : Go to  F6.
5. F5 CHECK THE PCM RPM SIGNAL INPUT 
   • Enter the following diagnostic mode on the diagnostic tool: PCM DataLogger
   • Key in START position.
   • Monitor the PCM engine speed (RPM) PID while operating the engine at 1,000 RPM, 1,500 RPM and 2,000 RPM.
   • Does the PCM PID match the tachometer indication? 
   1. YES  : Go to  F6.
   2. NO  : Go to  F7.
6. F6 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.
7. F7 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.