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Test 1: Vehicle Reference Voltage (VREF)

VEHICLE REFERENCE VOLTAGE (VREF)

TEST 1 VEHICLE REFERENCE VOLTAGE (VREF)
STEP INSPECTION ACTION
1 IS VREF GREATER THAN 6.0 VOLTS?
  • Disconnect TP sensor.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF (BR/W) and SIG RTN (GY/R) circuits at TP sensor connector.
  • Is VREF voltage greater than 6.0 volts? 
 Yes CHECK for VREF short to power.
Go to step 16.
No Go to next step.
2 CHECK BATTERY VOLTAGE
  • Key ON, Engine OFF (KOEO).
  • Is voltage across battery terminals greater than 10.5 volts? 
 Yes Go to next step.
No Key OFF.
See PINPOINT TEST 8: BATTERY CONDITION TEST  .
3 CHECK SIG RTN CIRCUIT TO SENSOR WHERE VREF CHECK FAILED
  • Key ON, Engine OFF (KOEO).
  • Disconnect sensor where VREF check failed.
  • Measure voltage between battery positive terminal and SIG RTN (O) circuit at appropriate sensor connector.
  • Is voltage greater than 10.5 volts and within 1.0 volt of battery voltage? 
 Yes Go to next step.
No SIG RTN/PWR GND fault present.
Go to step 11.
4 CHECK VREF INTEGRITY THROUGH PCM COMMUNICATION ON TP PID
  • Key ON, Engine OFF (KOEO).
  • Attempt to access the TP PID.
  • Can TP PID be accessed? 
 Yes Go to step 10 to check VREF for opens.
No Go to next step to check VPWR and VREF for shorts.
5 CHECK FOR VPWR TO IAC VALVE
  • Key OFF.
  • Disconnect IAC valve solenoid connector.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VPWR (W/R) circuit at IAC valve solenoid connector and battery negative terminal.
  • Is the voltage greater than 10.5 volts? 
 Yes RECONNECT IAC valve.
Go to next step.
No VPWR is not present.
RECONNECT TP sensor.
See TEST 6: PCM POWER RELAY  .
6 CHECK FOR SHORTED DPFEGR SENSOR
  • Key OFF.
  • Disconnect DPFEGR sensor (3.0L) or the EGR System Module (2.3L).
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF (BR/W) and SIG RTN (GY/R) circuits at TP sensor connector.
  • Is voltage between 4.0 and 6.0 volts? 
 Yes REPLACE DPFEGR sensor (3.0L) or the EGR System Module (2.3L).
See DIFFERENTIAL PRESSURE FEEDBACK EXHAUST GAS RECIRCULATION (EGR) SYSTEM - SENSOR .
RERUN PCM Quick Test.
See PCM QUICK TEST  .
No Go to next step.
7 CHECK FOR SHORTED FTP SENSOR
  • Key OFF.
  • Disconnect FTP sensor.
  • Disconnect DPFEGR sensor.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF (BR/W) and SIG RTN (GY/R) circuits at TP sensor connector.
  • Is voltage between 4.0 and 6.0 volts? 
 Yes REPLACE fuel tank pressure sensor.
See PCM QUICK TEST  .
RERUN PCM Quick Test.
No Go to next step.
8 CHECK VPWR TO PCM
  • Disconnect FTP sensor.
  • Disconnect PCM.
  • Install breakout box, leave PCM disconnected.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between test pin 35 (VPWR) and test pin 10 (PWR GND) at breakout box.
  • Is voltage greater than 10.5 volts? 
 Yes Go to next step.
No REPAIR open VPWR circuit between PCM and splice to IAC valve.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
9 CHECK VREF CIRCUIT FOR SHORT TO GROUND OR SIG RTN
  • Key OFF.
  • Disconnect WDS or equivalent tester from DLC.
  • Measure resistance between PCM test pin E40 (VREF) and test pin B10 (PWR GND) and E41 (SIG RTN) at breakout box.
  • Measure resistance between PCM test pin E40 (VREF) and test pin E41 (SIG RTN).
  • Is each resistance greater than 10,000 ohms? 
 Yes REPLACE PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Restore vehicle.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
No REPAIR VREF short to ground.
RESTORE vehicle.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
10 CHECK VREF CIRCUIT RESISTANCE TO PCM
  • Key OFF.
  • Disconnect PCM.
  • Install breakout box, leave PCM disconnected.
  • Measure resistance between test pin E40 (VREF) at breakout box and VREF circuit (BR/W) at the appropriate sensor connector.
  • Is resistance less than 5.0 ohms? 
 Yes REPLACE PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
RERUN PCM Quick Test.
See PCM QUICK TEST  .
No REPAIR open VREF circuit.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
11 CHECK SIG RTN/PWR GND THROUGH PCM ON TP PID
NOTE:
  • The purpose of this step is to determine if the WDS or equivalent tester is able to communicate with the PCM.
  • Key ON, Engine OFF (KOEO).
  • Attempt to access the TP PID.
  • Can the PID be accessed? 
 Yes Go to next step.
No Go to step 14.
12 ARE KOEO DTCS PRESENT FOR TWO OR MORE SENSORS/SWITCHES CONNECTED TO THE SIG RTN CIRCUIT?
  • Sensors connected to SIG RTN:
    • ECT sensor, IAT sensor, CMP sensor, DPFE sensor, FTP sensor, CPP switch/jumper, TFT sensor, TSS sensor, PSP switch and O2 sensors #1, #2, #3, and #4.
  • Are KOEO DTCs present for two or more components connected to SIG RTN circuit? 
 Yes Go to next step.
No REPAIR open SIG RTN circuit to component where VREF check failed.
RERUN Quick Test.
See PCM QUICK TEST  .
13 CHECK SIG RTN CIRCUIT RESISTANCE TO PCM
  • Key OFF.
  • Disconnect WDS or equivalent tester from DLC.
  • Disconnect PCM.
  • Install breakout box, leave PCM disconnected.
  • Measure resistance between test pin E41 (SIG RTN) at breakout box and SIG RTN (GY/R) circuit at the appropriate sensor connector.
  • Is resistance less than 5.0 ohms? 
 Yes RECONNECT sensor.
Go to next step.
No REPAIR open SIG RTN circuit.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
14 CHECK PCM PWR GND CIRCUITS
  • Key OFF.
  • Disconnect WDS or equivalent tester from DLC.
  • Disconnect PCM.
  • Install breakout box, PCM disconnected.
  • Measure resistance between battery negative terminal and test pins B47, B48, B49, and B10 (PWR GND) at breakout box.
  • Is each resistance less than 5.0 ohms? 
 Yes Go to next step.
No REPAIR open circuit.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
15 CHECK GROUND CIRCUITS IN PCM
  • Key OFF.
  • Connect PCM to breakout box.
  • Measure resistance between PCM test pin E41 (SIG RTN) and test pins B47, B48, B49, and B10(PWR GND).
  • Is each resistance less than 5.0 ohms? 
 Yes SIG RTN/PWR GND circuits are OK.
VERIFY results from previous test steps.
RERUN PCM Quick Test to verify DTC/symptom.
See PCM QUICK TEST  .
No REPLACE PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Rerun PCM Quick Test.
See PCM QUICK TEST  .
16 CHECK VREF FOR SHORT TO POWER
  • Key OFF.
  • Disconnect sensor connector where VREF check failed.
  • Disconnect all other sensors connected to VREF circuit (TP, DPFE and FTP sensor).
  • Disconnect PCM.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between the VREF (BR/W) circuit at TP sensor connector and the battery negative terminal.
  • Is voltage less than 0.5 volts? 
 Yes REPLACE PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
RERUN PCM Quick Test.
See PCM QUICK TEST  .
No REPAIR VREF short to power in harness.
RERUN PCM Quick Test.
See PCM QUICK TEST  .
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