Diagnostic Starting Point - Engine Controls
Begin the system diagnosis with Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check-Vehicle will provide the following information
- The identification of the control modules which command the system
- The ability of the control modules to communicate through the serial data circuit
- 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
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Ignition ON/Engine OFF | |||
| Electronics Battery Fd | Data | Volts | 12.6 Volts |
| Load Shed | Inputs | None/Load 1//Load 2/Load 3 | None |
| Inadvertent Power Relay | Outputs | On/Off | Off |
| Load Management Relay | Outputs | On/Off | Off |
Body Control Module (BCM)
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Ignition ON/Engine OFF | |||
| Crank Request Signal | Engine Data 2 | Yes/No | No |
| GEN F-Terminal Signal | Engine Data 2 | % | 0% |
| GEN L-Terminal Signal Command | Engine Data 2 | On/Off | Off |
| Ignition 1 Signal | Engine Data 1 | Volts | 12.6 Volts |
| Starter Enable Relay Circuit Status | Output Driver Data | Fault/OK/Invalid State | OK |
| Starter Relay Command | Engine Data 2 | On/Off | Off |
Powertrain Control Module (PCM 3.4L LA1)
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Ignition ON/Engine OFF | |||
| Crank Request Signal | Electrical/Theft Data | Yes/No | No |
| GEN F-Terminal Signal | Electrical/Theft Data | % | 0% |
| GEN L-Terminal Signal Command | Electrical/Theft Data | On/Off | Off |
| Ignition 1 Signal | Electrical/Theft Data | Volts | 12.6 Volts |
| Starter Relay Command | Electrical/Theft Data | On/Off | Off |
Engine Control Module (ECM 3.6L LY7)
Scan Tool Data Definitions
The Engine Scan Tool Data Definitions contains a brief description of all engine 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 Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Crankshaft Position Variation Learn | Enables the powertrain control module (PCM) to learn the variations in the crankshaft position (CKP) system. The PCM will learn the variations once the following conditions are met: Engine coolant temperature (ECT) is more than a specific value All the instructions on the scan tool have been completed The accelerator pedal smoothly applied until the fuel cut-off, as specified on the scan tool, is achieved and then immediately released The PCM learns the variation values on the deceleration from the fuel cut-off. | |
| Cylinder Power Balance | Fuel System | Enables/Disables a cylinder by turning OFF the fuel injector to the cylinder. The fuel injector is normally enabled. The PCM disables the fuel injector when the following conditions are met: All instructions on the scan tool are completed. Stabilized engine speed Fuel injector selected When DISABLE is selected, the PCM turns the injector OFF for 30 seconds. During this period, the engine operates with a misfire. |
| EGR Solenoid | Engine Output Controls | Activates the exhaust gas recirculation (EGR) solenoid in 10 percent increments from 0 to 100 percent or a maximum of 30 seconds at 100 percent. |
| Engine Speed Control | TAC System | Activates the throttle activation control (TAC) system to change engine RPM. The normal commanded state is None. To enable the RPM control, all instruction on the scan tool must be completed. The system will increase or decrease the RPM within a range of 350-2,000 RPM. The set step value changes the RPM by increments of 25 RPM, 100 RPM, and 500 RPM. The system remains in the commanded state until cancelled by the scan tool. |
| EVAP Purge Solenoid | Engine Output Controls/EVAP System | Activates the purge solenoid in 10 percent increments from 0 to 100 percent. The device control will be aborted and inhibited if the fuel tank pressure (FTP) sensor exceeds 19 mm Hg (10 in H2O). |
| EVAP Vent Solenoid | Engine Output Controls/EVAP System | Activates the vent solenoid. The device control will be aborted and inhibited if the FTP sensor exceeds 19 mm Hg (10 in H2O). |
| EVAP Purge/Seal | Engine Output Controls/EVAP System | Simultaneously activates the purge solenoid in 10 percent increments from 0 to 100 percent and the vent solenoid. The device control will be aborted and inhibited if the FTP sensor exceeds 19 mm Hg (10 in H2O). |
| Fuel Injector Balance | Fuel System | Enables the fuel injector in order to verify proper fuel injector flow. The PCM will pulse the selected injector when the following conditions are met: All instruction on the scan tool completed. Fuel injector selected Key ON, engine OFF The selected fuel injector can only be flowed/pulsed once per ignition cycle. |
| Fuel Pump | Engine Output Controls | Activates the fuel pump relay for 2 seconds. Also turns fuel pump ON and OFF while engine is running. |
| Fuel Trim Enable | Fuel System | Disables the PCMs ability to learn new fuel trim parameters. The commanded states are NONE, ENABLED, DISABLED. The normal commanded state is NONE. The system remains in the commanded state until cancelled by the scan tool. |
| Fuel Trim Reset | Fuel System | Activates the reset of fuel trim data in all fuel trim cells. |
| Loop Status | Engine Output Controls | Controls the system loop status. The commanded states include NONE, OPEN, or CLOSED. The normal commanded state is NONE. When commanded OPEN or CLOSED, the system remains in the commanded state until cancelled by the scan tool. |
| MIL | Engine Output Controls/Dash Lamps | Activates the malfunction indicator lamp (MIL). The MIL will remain illuminated until cancelled by the scan tool. |
| Misfire Graphic | Graphs the accumulated misfires occurring in each cylinder. The scan tool allows for a reset of the misfire graph. | |
| O2S Heater Control | Engine Output Controls | Activates the heated oxygen sensor (HO2S) heater. The commanded states include NONE, ON, and OFF. The normal commanded state is NONE. On a cold engine, with the key ON, engine OFF, the HO2S signal will continue to drop below bias when commanded ON. The system remains in the commanded state until cancelled by the tool. |
Powertrain Control Module Scan Tool Output Control
See also:
• Diagnostic System Check - Vehicle