Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Control System & Fuel System - 6.6l (Lmm) - Introduction (1 of 2) Chevrolet Chevy Express H1500

Diagnostic Starting Point - Engine Controls

Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information

  1. The identification of the control modules which command the system
  2. The ability of the control modules to communicate through the serial data circuit
  3. The identification of any stored diagnostic trouble codes (DTCs) and the codes' statuses

The use of the Diagnostic System Check - Vehicle will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Data List (Engine Control Module)

The Engine Control Module Scan Tool Data List contains all ECM related parameters that are available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists, and in some cases may appear more than once, or in more than one data list in order to group certain related parameters together.

Use the Engine Control Module Scan Tool Data List only after the following is determined

  1. The Diagnostic System Check - Vehicle is completed.
  2. No diagnostic trouble codes (DTCs) are present.
  3. The on-board diagnostics are functioning properly.

Scan tool values from a properly running engine may be used for comparison with the engine you are diagnosing. The Engine Control Module Scan Tool Data List represents values that would be seen on a normal running engine.

IMPORTANTA scan tool that displays faulty data should not be used. The scan tool problem should be reported to the manufacturer. Use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.

The column labeled Data List indicates where a parameter can be located on the scan tool. Refer to the scan tool operating manual for the exact locations of the data lists. The following is a description of each term listed

Scan Tool ParameterData ListUnits DisplayedTypical Data Value
Operating Conditions: Engine Idling/Lower Radiator Hose Hot/Closed Throttle/Park or Neutral/Accessories Off
5-Volt Reference 1 CircuitExh.OK/FaultOK
5-Volt Reference 2 CircuitExh.OK/FaultOK
5-Volt Reference 3 CircuitExh.OK/FaultOK
A/C Relay CommandEng, EGRON/OFFOff
Ambient Air Temp.Eng°C (°F)Varies
APP Indicated AngleEng, EGR, Fuel, FF/FR%0.0
APP Sensor 1Eng SpdVolts0.90-0.94
APP Sensor 1 Indicated PositionEng Spd%0%
APP Sensor 2Eng SpdVolts0.40-0.50
App Sensor 2 Indicated PositionEng Spd%0%
Balancing Rate Cyl. 1-8Eng, FuelMm 34.0 to +4.0
BAROEng, EGR, FF/FRKPa65-104 (Varies with altitude)
Base Injector Fuel RateEng FuelMm 35-7
Boost Pressure SensorEng Spd, IndKPaBARO
CAM Signal PresentEng. Pos.Yes/NoYes
CKP Sensor Signal PresentEng. Pos.Yes/NoYes
Cmmd. A/F Equivalence RatioEng, Exh, Fuel, IndRatio0:2:1
Coolant Level SwitchEngOK/LowOK
Cruise Control ActiveEng.Yes/NoNo
Current Fuel TypeFuelDieselDiesel
Desired EGR PositionEGR%20-50
Desired Fuel Rail PressureEng, Fuel, EGRMPa/PSI25-35 MPa (3,626-5,076 psi)
Desired IAF Valve PositionEGR, Exh, Induc.%100
Desired Idle SpeedEng 1, FF/FRRPM630-700
Desired TC BoostInduc., Eng, Spd.KPaBARO
Des. TC Vane PositionTC%80-100
Des. TC Vane Pos. Ctrl. SolenoidTCAmps0.0
Distance Since DTC ClearedEngKm/miles0
Distance Since Last DPF RegenerationExhKm/milesVaries
DPF Indicator CommandExh.ON/OFFOFF
DPF Pressure SensorExh.Volts0.97-1.3
DPF Regen Inhibit ReasonExh.ReasonReason
DPF Regeneration ReasonExh.ReasonReason
DPF Regeneration StatusExh.StatementNot Required
DPF Soot MassExh.Grams0-10
EC Ignition Relay CommandEng, Eng Spd.ON/OFFON
ECT Sensor 1All°C (°F)105-185°C (221-365°F)
ECT Sensor 2Eng°C (°F)105-185°C (221-365°F)
EGR Learned Minimum PositionEGR%0
EGR Position SensorEGRVolts1-1.1
EGR Position SensorEng%20
EGR Position VarianceEGR%Varies
EGR Solenoid CommandEGR%5-15
EGT Sensor 1Exh.°C (°F)80-120°C (176-248°F)
EGT Sensor 2Exh.°C (°F)80-120°C (176-248°F)
Engine LoadAll%1%
Engine Oil Life RemainingEng 1%Varies
Engine Oil Pressure SensorFuelKPa/PSIVaries
Engine Run TimeAllHrs/Mins/SecVaries with engine run time
Engine Run Time Since Last DPF RegenerationExh.HH:MM:SSVaries
Engine SpeedAllRPM+/-50 RPM from desired
FRP Regulator CommandEng, Fuel, EGR, FF/FR%35-45
Fuel Level SensorFuelVoltsVaries with fuel level
Fuel Pump Relay CommandEng, FuelON/OFFOFF
Fuel Rail Pressure SensorEng, FuelMPa25-35 MPa (3,626-5,076 psi)
Fuel Rail Pressure SensorFuelVolts1-2
Fuel Tank Level RemainingEng, Exh., Fuel, Mis.%Varies
Fuel Temperature SensorEng, Fuel, FF/FR°C/°F10-90°C (50-194°F)
Fuel Used Since Last DPF RegenerationExh.Liters/Gallons3.78/1 (1 regen complete)
Glow Plug CommandEng, Ind.ON/OFFOFF
High Idle SwitchEng. Spd.On/OffOff
IAF Valve Learned MinimumInd.%100
IAF Valve PositionEGR, Exh., Ind.%100
IAF Valve Pos. SensorInd.Volts4-5 Volts
IAT Sensor 1Eng 1, EGR, TC, FF/FR°C/°F10-90°C (50-194°F) (temperatures may increase under heavy engine loads)
IAT Sensor 2Eng 1, EGR, TC, FF/FR°C/°F10-90°C (50-194°F) (temperatures may increase under heavy engine loads)
Ignition Accessory SignalEng, Eng. Spd.ON/OFFOFF
Ignition 1 SignalEng 1, EGR, FF/FRVoltsBattery voltage (accuracy +/-0.4 volts)
Ignition 1 SignalAllVolts12-14
Injection Pump CAM Reference Signal MissedEng. Pos., FuelCounts0
Injector TimingEng, Fuel°
Intake Air Heater CommandExh., Ind.%0
Intake Air Heater CommandInd.ON/OFFOFF
MAF SensorInd.Hz2400-1700
MAP SensorEng, IndGramsVaries
Misfire Current Cyl. 1Mis.Counts0
Misfire Current Cyl. 2Mis.Counts0
Misfire Current Cyl. 3Mis.Counts0
Misfire Current Cyl. 4Mis.Counts0
Misfire Current Cyl. 5Mis.Counts0
Misfire Current Cyl. 6Mis.Counts0
Misfire Current Cyl. 7Mis.Counts0
Misfire Current Cyl. 8Mis.Counts0
Particulate Filt. Pressure VarianceEng. Spd., Exh., Ind.KPa0.0-3.5
Pilot Inj. Cyl. 1-8 CommandEngOn/OffOn
PNP SwitchEngIn Gear/Park/NeutralPark/Neutral
Reduced Engine PowerCyl. Dea., Eng. Spd., FuelInactive, ActiveInactive
Start up ECTCool°C/°FVaries (ECT at time of engine startup)
Start Up Fuel TemperatureFuel°C/°FVaries
Start up IATCool°C/°FVaries (IAT at time of engine startup)
TC Vane Position Lrn. this run cycleIndYes/NoYes
TC Vane Position Lrn. Since DTC ClearIndYes/NoYes
TC Vane Position SensorInd%70-100
TC Vane Position SensorInd.Volts2-4
TC Vane Pos. Ctrl. SolenoidIndDC40-50
TCC/Cruise Brake Pedal SwitchEngApplied/ReleasedReleased
Vehicle Speed SensorAllMph/km/h0
Warm-ups Since DTC ClearedEngCounts1
Warm-ups w/o Emission FaultsEngCounts0
Warm-ups w/o Non-Emission FaultsEngCounts0
Water In Fuel SensorFuelWater/ No WaterNo Water
Water In Fuel SensorFuelVolts0.21-4.75

Scan Tool Data List

Scan Tool Data List (Glow Plug Control Module)

The GPCM Scan Tool Data List contains all glow plug control module related parameters that are available on the scan tool. The list is arranged in alphabetical order.

Use the GPCM Scan Tool Data List only after the following is determined

  1. The Diagnostic System Check - Vehicle is completed.
  2. No diagnostic trouble codes (DTCs) are present.
  3. The on-board diagnostics are functioning properly.

Scan tool values from a properly running engine may be used for comparison with the engine you are diagnosing. The GPCM Scan Tool Data List represents values that would be seen on a normal running engine.

IMPORTANTA scan tool that displays faulty data should not be used. The scan tool problem should be reported to the manufacturer. Use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.
Scan Tool ParameterUnits DisplayedTypical Data Value
Operating Conditions: Engine Idling/Lower Radiator Hose Hot/Closed Throttle/Park or Neutral/Accessories Off
Glow PlugVolts14
Glow Plug 1-8Amps19-21
Glow Plug 1-8Ohms0.49-0.90
Glow Plug Driver OpenOK/FaultOK
Glow Plug Driver ShortedOK/FaultOK
Glow Plug OvertempOK/FaultOK
Glow Plug OvervoltageOK/FaultOK
Glow Plug UndervoltageOK/FaultOK
IA Heater Driver CurrentOK/FaultOK
IA Heater Driver GroundedOK/FaultOK
IA Heater Driver OpenOK/FaultOK
IA Heater Driver ShortedOK/FaultOK
IA Heater OvertempOK/FaultOK
IA Heater OvervoltageOK/FaultOK
IA Heater UndervoltageOK/FaultOK
Ignition 1 SignalVoltsBattery Voltage
Intake Air HeaterVolts11-13.2
Intake Air Heater%0

Scan Tool Data List

Scan Tool Data Definitions

The Engine Control Module Scan Tool Data Definitions contains a brief description of all engine control module (ECM) related parameters available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together.

Scan Tool Output Controls

Scan Tool Output ControlAdditional Menu Selection(s)Description
Balance Rate MonitorFuel SystemThis function will allow actual balance rate values to be displayed.
Cylinder Power BalanceFuel SystemDisables each fuel injector. Device Control can be changed at any engine or vehicle speed. The device control will not change unless changed or cancelled by the scan tool.
DPF Regeneration EnableExh.This function enables a DPF Regen when the vehicle meets the conditions for running. This function will by-pass the normal soot model, so the next time the vehicle is under the conditions for an active regeneration to take place, the ECM will go ahead and initiate the regeneration event.
DPF Reset Replace DPFOutput ControlsResets all DPF parameters to zero.
DPF Service RegenerationExh.This function enables a DPF Regen. The engine coolant must be greater than 70-115°C (158-239°F). Vehicle must be in Park. Ambient temperature must be greater than -30°C (-22°F). Brake pedal and accelerator must be in the released position. The scan tool will display all inhibit reasons. The scan tool must remain connected until test is complete. This function takes approximately 35 minutes to complete. During this procedure the RPM will slowly increase to 2,500 RPM and remain there for approximately 25 minutes.
EGR SolenoidOutput ControlsActivates the exhaust gas recirculation (EGR) solenoid ON or OFF. The EGR position is limited to 40 percent duty cycle, which is 100 percent commanded open valve. The device control is limited to 10 seconds ON, with a 10 second OFF cooling time. This device control is disabled by DTC P0403.
Engine Speed ControlSpecial Functions/Engine Speed/ThrottleAdjusts the engine speed in 25, 100, or 500 RPM increments between 600-1500 RPM. The Device Control will not change unless changed or cancelled by the scan tool.
Fuel Pressure ControlFuel SystemChanges the Fuel Pressure in 5 MPa increments from 30-160 MPa. The Device Control will not change unless changed or cancelled by the scan tool. This device control is disabled if any of the following conditions are met: Engine speed is more than 2500 RPM. Vehicle Speed is more than 40 km/h (25 mph).
Fuel PumpEngine Output ControlsActivates the fuel transfer pump or prime pump (depending on application) ON or OFF. The Device Control will not change unless changed or cancelled by the scan tool.
Fuel Transfer Pump RelayFuel SystemThis function commands the fuel transfer pump relay ON/OFF.
IAF Valve MotorInd.This function increases or decreases the position of the IAF valve.
Malfunction Indicator LampOutput ControlsActivates the malfunction indicator lamp (MIL). The MIL will remain illuminated until cancelled by the scan tool.
Pilot Injector Balance ProcedureFuel SystemDisables each fuel injector pilot injection. Device Control can be changed at any engine or vehicle speed. The device control will not change unless changed or cancelled by the scan tool.
TC Vane Position SensorOutput ControlsAdjusts the turbocharger vane position in 5 percent increments from 0-100 percent. The device control will be aborted if engine speed is above idle or if the coolant temperature is too cold.
TC Vane SolenoidOutput ControlsCycles the turbocharger vane position solenoid to 100 percent boost and back to 0 percent boost. The device control is limited to engine speeds less than 1,500 RPM and will be disabled if DTC P0045 is set.

Scan Tool Output Controls