Diagnostic Starting Point - Engine Controls
Begin the system diagnosis with Diagnostic System Check - Engine Controls . The Diagnostic System Check-Engine Controls 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-Engine Controls will identify the correct procedure for diagnosing the system and where the procedure is located.
Description
The Diagnostic System Check is an organized approach to identifying a condition created by an electronic engine control system malfunction. The Diagnostic System Check must be the starting point for any driveability concern. The Diagnostic System Check directs the service technician to the next logical step in diagnosing the concern. Understanding the table and using the table correctly reduces diagnostic time and prevents the replacement of good parts.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Perform the following preliminary inspections: Ensure that the battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical. Ensure that the battery cables are clean and tight. Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom. Refer to Strategy Based Diagnosis in General Information Ensure that the engine and control module grounds are clean, tight, and in the correct location. Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems. Did you find and correct the condition? | System OK | Go to Step 2 |
| 2 | Install a scan tool. Turn ON the scan tool. Does the scan tool turn ON? | Go to Step 3 | Go to Scan Tool Does Not Power Up in Data Link Communications |
| 3 | Turn ON the ignition, with the engine OFF. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information using the Class 2 Message Monitor feature: Engine control module (ECM) Electronic brake control module (EBCM) Body control module (BCM) Does the scan tool communicate with all the listed modules? | Go to Step 4 | Go to Data Link References in Data Link Communications |
| 4 | IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Refer to the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position. Does the ignition switch parameter reading match the ignition switch position for all switch positions? | Go to Step 5 | Go to Power Mode Mismatch in Body Control System |
| 5 | Attempt to start the engine. Does the engine crank? | Go to Step 6 | Go to Symptoms - Engine Electrical in Engine Electrical |
| 6 | Did the engine start and idle? | Go to Step 7 | Go to Engine Cranks but Does Not Run |
| 7 | IMPORTANT: Do NOT clear the DTCs unless instructed by a diagnostic procedure. Select the DTC display function for the following control modules and record the DTCs: ECM EBCM BCM If multiple powertrain DTCs are stored, diagnose the DTCs in the following order: Component level DTCs. For example, sensor DTCs, solenoid DTCs, and relay DTCs. Begin with the lowest number DTC unless the diagnostic table directs you otherwise. System level DTCs. For example, misfire DTCs, EVAP system DTCs, fuel trim DTCs, and system voltage DTCs. Search for applicable service bulletins. Does the scan tool display any DTCs? | Go to Step 8 | Go to Step 10 |
| 8 | If there are any powertrain DTCs, select Capture Info to store the powertrain DTC information with a scan tool. Did you complete the action? | Go to Step 9 | |
| 9 | Does the scan tool display DTCs which begin with a "U"? | Go to Data Link References in Data Link Communications | Go to Diagnostic Trouble Code (DTC) List for applicable diagnostic procedure |
| 10 | Is the customer's concern with Inspection/Maintenance (I/M) testing? | Go to Inspection/Maintenance (I/M) System Check | Go to Step 11 |
| 11 | Are there any driveability symptoms observed? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. |
| IMPORTANT |
|---|
| Do NOT clear the DTCs unless instructed by a diagnostic procedure. |
Diagnostic System Check - Engine Controls
Scan Tool Data List
The Engine Scan Tool Data List contains all engine related parameters that are available on the scan tool. The list is arranged in alphabetical order. A 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 Scan Tool Data List only after the following conditions are determined
- The Diagnostic System Check-Engine Controls is completed.
- There are no diagnostic trouble codes (DTCs).
- 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 Scan Tool Data List represents the values that would be seen on a normal running engine.
| IMPORTANT | Do not use a scan tool that displays faulty data. The scan tool concern should be reported to the manufacturer. Use of a faulty scan tool can result in misdiagnosis and in unnecessary parts replacement. |
Only the parameters listed below are referenced in this service manual for use in diagnosis. If all values are within the typical range described below, refer to Symptoms - Engine Controls for diagnosis.
The column labeled Data List indicates where a parameter is located on the scan tool. Review the scan tool operating manual for the exact locations of the data lists. The following is a description of each term listed
| Scan Tool Parameter | Data List | Parameter Range/Units | Typical Data Values |
|---|---|---|---|
| Engine Idling/Radiator Hose Hot/Park or Neutral/Closed Loop/Accessories Off | |||
| A/C High Side Pressure | Eng 1, 2, FR | 0-3,450 kPa / 0-500 psi | Varies |
| A/C High Side Pressure Sensor | Eng 1, 2 | 0-5 Volts | Varies |
| A/C Off for WOT | Eng 1, TAC | Yes/No | No |
| A/C Pressure Disable | Eng 1 | Yes/No | No |
| A/C Relay Command | Eng 1, 2, 3 | On/Off | Off |
| A/C Request | Eng 1, 2 | Yes/No | No |
| Air Fuel Ratio Bank 1 or Bank 2 | Ft | 14.7:1 | 14.7:1 |
| APP Angle | Eng 1, 2, EVAP, FT, FR, MF, TAC | 0-99% | 0 percent at idle |
| APP at Idle | TAC | 0-99% | Varies |
| APP Sensor 1 | TAC | 0.9-4.5 Volts | 1 Volt |
| APP Sensor 2 | TAC | 0.45-2.25 Volts | 0.5 Volt |
| Battery Voltage | Eng 1, 2, 3, EVAP, TAC | 0-25.5 Volts | 12.8-14.2 Volts |
| Calculated Baro | Eng 1, EVAP, FT | 65-104 kPa -16 psi | Varies with altitude |
| Calc. Converter Temp. (most accurate after warm-up, cruising) | Eng 1, FT | 40 to + 950°C /-40 to + 1742°F | 600-900°C/1112-1652°F |
| Catalyst Overtemp Bn. 1 | FT | Yes/No | No |
| Catalyst Overtemp Bn. 2 | FT | Yes/No | No |
| * Clutch Start Switch (If Equipped) | Eng 1, 2, TAC | On/Off | Off |
| CMP Active Counter | Eng 2 | 0-256 Counts | Varies |
| Cooling Fan After Run | Eng 3, FR | Requested/Not Requested | Not Requested |
| Commanded Cooling Fan | Eng 2, 3, FR | Off/Low/High and Aux if Equipped | Off |
| Crank Request | Eng 1, 3 | Yes/No | No |
| * Cruise Clutch Switch (If Equipped) | Eng 1, 3, TAC | Applied/Released | Released |
| Cruise Engaged | Eng 1, 2, 3, FR, TAC | Yes/No | No |
| Cruise On/Off Switch | TAC, FR | On/Off | Off |
| Cruise Release Brake Pedal Switch | Eng 1, 3, TAC, FR | Applied/Released | Released |
| Cruise Resume/Accel. Switch | TAC, FR | On/Off | Off |
| Cruise Set/Coast Switch | TAC, FR | On/Off | Off |
| Cruise VSS Out of Range | Eng 3, TAC, FR | Yes/No | Yes |
| Current Gear | Eng 1, 2, 3, FR, FT | P/N/R/1-5 | P/N |
| Decel. Fuel Cutoff | Eng 2, FR, FT | Active/Inactive | Inactive |
| Delivered Torque PWM Duty Cycle | Eng 2 | 0-100% | 10% |
| Desired Idle Speed | Eng 1, 2, 3, EVAP, FR, TAC | 0-7,000 RPM | 650 RPM |
| Distance Since First Failure | FR | Km/mi | Varies |
| DTC No. 1 | Eng 1, EVAP, FT, TAC | PXXXX | Varies |
| DTC No. 2 | Eng 1, EVAP, FT, TAC | PXXXX | Varies |
| ECM in VTD Fail Enable VTD | Eng 3 | Yes/No | No |
| ECT | Eng 1, 2, 3, EVAP, FF, FR, FT, MF | 39 to +140°C/-38 to +284°F | 85-105 °C/185-220°F |
| Engine At Operating Temperature | FR | Yes/No | Varies |
| Engine Drag Control Active | TAC | Yes/No | Yes |
| Engine Idling | FR | Yes/No | Yes |
| Engine Load | Eng 1, FF | 0-99% | 2% |
| Engine Oil Life Remaining | Eng 3 | 0-100% | Varies |
| Engine Oil Level Switch | Eng 2, 3 | OK/Low | OK |
| Engine Oil Pressure Switch | Eng 3, FR | OK/Low | OK |
| Engine Run Time | ALL | 0:00:00 | Varies |
| Engine Speed | ALL | RPM | 650 RPM |
| EVAP Canister Purge | Eng 1, EVAP, FR, FT | 0-100% | Varies |
| EVAP Vent Solenoid | Eng 1, EVAP, FR, FT | On/Off | Off |
| Extended Travel Brake Pedal Switch | Eng 1, 2, 3, TAC | Applied/Released | Released |
| Fast idle for A/C Performance | Eng 1, TAC | Active/Inactive | Inactive |
| Fast Idle for Cold Start | TAC | Active/Inactive | Inactive |
| Fast Idle for Generator Performance | Eng 2, TAC | Active/Inactive | Inactive |
| Fast Idle for Heater Performance | TAC | Active/Inactive | Inactive |
| Fast Idle for Hot Start | TAC | Active / Inactive | Inactive |
| Fuel Level | Eng 1, EVAP, FR, MF | Gal/L | Varies |
| Fuel Level Sensor Left Tank | Eng 1, EVAP | 0-5 Volts | Varies |
| Fuel Level Sensor Right Tank | Eng 1, EVAP | 0-5 Volts | Varies |
| Fuel Pump Relay Command | Eng 1, FR | On/Off | On |
| Fuel Tank Pressure | Eng 1, EVAP | In H2O/mm Hg | Varies |
| Fuel Tank Pressure Sensor | Eng 1, EVAP, FR | 0-5 Volts | Varies |
| GEN L-Terminal Signal Command | Eng 2, FR | On/Off | On |
| GEN F-Terminal Signal | Eng 2 | % | On |
| HO2S Bank 1 or Bank 2 Sensor 1 | Eng 1,2, EVAP, FF, FR, FT | 0-4,998 mV | Varies between 30-800 mV |
| HO2S Bank 1 or Bank 2 Sensor 2 | Eng 1, 2, EVAP, FF, FR, FT | 0-4,998 mV | Varies 400-700 mV |
| HO2S Heater Bn 1 or Bn 2 Sen. 1 | FT | High/Low | Varies |
| HO2S Heater Bn 1 or Bn 2 Sen. 2 | FT | High/Low | Varies |
| HO2S Heater Bn 1 or Bn 2 Sen. 1 | FT | 0-99% | Varies |
| HO2S Heater Bn 1 or Bn 2 Sen. 2 | FT | 0-99% | Varies |
| IAT | Eng 1, 2, 3, EVAP, FF, FR, FT, MF | 39 to +140°C/-38 to +284°F | Varies |
| Ignition 0 | Eng 1, 3, EVAP, FT, TAC | 0-25.5 Volts | 12.8-14.2 Volts |
| Ignition 1 | Eng 1, 2, 3, EVAP, FR, FT, MF, TAC | 0-25.5 Volts | 12.8-14.2 Volts |
| Ignition Dwell | Eng 1 | 1-4 ms | 1.9 ms |
| Ignition State | Eng 1 | On/Cranking/Off | On |
| Inj. PWM Average Bank 1 or Bank 2 | Eng 2, 3, EVAP, FT | 0-9 ms | 3.0-5.4 ms |
| Intake Manifold Tuning (IMT) Valve Solenoid | Eng 2, FR | Open/Closed | Closed |
| Intake Manifold Runner Control (IMRC) Solenoid | Eng 2, FR | Open/Closed | Open |
| Knock Control | Eng 1, FR | Active/Inactive | Inactive |
| Knock Sensor 1 | Eng 1 | 0.25-2.67 Volts | 4.6-5.4 Volts |
| Knock Sensor 2 | Eng 1 | 0.25-2.67 Volts | 4.6-5.4 Volts |
| Knock Retard Cyl. 1-6 | Eng 1 | 0-191 Degrees | 0 Degrees |
| LT FT Bn. 1 or Bn. 2 Cruise/Accel. | Eng 1, 2, 3, EVAP, FF, FR, FT | 100 to 100% | 0% |
| LT FT Bn. 1 or Bn. 2 Idle/Decel. | Eng 1, 2, 3, EVAP, FR, FT | 100 to +100% | 0% |
| Loop Status Bank 1 or Bank 2 | Eng 1, 2, 3, EVAP, FF, FR, FT | Open/Closed | Closed |
| MAF | Eng 1, 2, 3, EVAP, FF, FR, FT, MF, TAC | 0-655 g/s | 3.4-6.3 g/s |
| MAF Sensor | Eng 1, 3, FR, MF, TAC | 0-5 Volts | 1.2-1.5 Volts |
| Main Relay Command | Eng 1 | On/Off | On |
| MIL | Eng 1 | On/Off | Off |
| MIL Flashing | Eng 1 | Yes/No | No |
| Mileage Since DTC Cleared | Eng 1, 3 | Km/mi | Varies |
| Mileage Since MIL Request | Eng 1 | Km/mi | Varies |
| Misfire Current Cyl. 1-6 | MF | 0-255 Counts | 0 |
| Misfire History Cyl. 1-6 | MF | 0-255 Counts | 0 |
| Number of DTC(s) | Eng 1, EVAP, FT, TAC | # | 0 |
| Password Learning Enabled | Eng 3 | On/Off | Off |
| * PNP Switch (If Equipped) | Eng 2, 3, TAC | In Gear /Park/Neutral | Park/Neutral |
| Power Enrichment | Eng 2, FR, FT | Active/Inactive | Inactive |
| Power Management (TAC Error) | Eng 3, TAC | Active/Inactive | Inactive |
| Reduced Power (TAC Error) | Eng 3, TAC | Active/Inactive | Inactive |
| Requested Torque PWM Duty Cycle | Eng 2, TAC | 0-99% | 90% |
| Rough Road Detection | Eng 2, MF | Present/Not Present | Not Present |
| Short Term FT Bank 1 or Bank 2 | Eng 1, 2, 3, EVAP, FF, FR, FT | 100 to +100% | 3% to +3% |
| Spark Advance | Eng 1, 2, 3, FF, FT | 133 to +78 Degrees | 2-5 Degrees |
| Starter Relay Command | Eng 1, 3 | On/Off | Off |
| Start Up ECT | Eng 2, EVAP, FR, FT | 39 to +140°C/-38 to +284°F | Varies |
| Start Up IAT | Eng 2, EVAP, FT | 39 to +140°C/-38 to +284°F | Varies |
| Stoplamp Pedal Switch | Eng 1, 2, 3, FR, TAC | Applied/Released | Released |
| TAC Forced Engine Idle | Eng 3, TAC | Active/Inactive | Inactive |
| TAC Learn Counter | TAC | 0-255 Counts | Varies |
| TAC Limit Power | Eng 1, TAC | Yes/No | No |
| Throttle Actuator DC | Eng 1, TAC | 0-99% | Varies |
| Throttle Plate at Idle | TAC, FR | Yes/No | Yes |
| Throttle Plate at WOT | TAC, FR | Yes/No | No |
| TP 1 Learned Min | TAC | 0-5 Volts | 0-0.5 Volts |
| TP 2 Learned Min | TAC | 5-0 Volts | 5-3.7 Volts |
| TP Angle | Eng 1, 2, 3, EVAP, FF, FR, FT, MF, TAC | 0-99% | 0 percent |
| TP Desired Angle | Eng 1, 2, EVAP, FT, TAC | 0-99% | Varies |
| TP Sensor 1 | Eng 1, 2, 3, TAC | 0-5 Volts | 0.5-0.8 Volts |
| TP Sensor 2 | Eng 1, 2, 3, TAC | 0-5 Volts | 4.1-4.5 Volts |
| Vehicle Speed | Eng 1, 2, 3, EVAP, FF, FR, FT, MF, TAC | Km/mi | Varies |
| Volumetric Efficiency | Eng 1,2,3, EVAP, FR, FT, TAC | 0-100% | 13% |
Scan Tool Data List
Scan Tool Data Definitions
The Scan Tool Data Definitions list contains a brief description of all of the engine 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. 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 |
|---|---|---|
| Engine Speed Control | Special Functions/TAC System | This function activates the idle speed override in 20 RPM, 100 RPM, and 500 RPM increments, from 600 RPM to 1700 RPM. The engine speed will remain in the commanded state until cancelled by the tool. |
| EVAP Purge Solenoid (PWM) | Special Functions/EVAP System | This function activates the EVAP purge solenoid valve. The normal commanded state is NONE. The system will INCREASE or DECREASE the amount of purge by changing the duty cycle of the purge valve in 10 percent increments within a range of 0 percent-100 percent. The system remains in the commanded state until cancelled by the tool or the fuel tank pressure (FTP) exceeds -24 mm Hg (-12 in H20). |
| EVAP Purge/Seal | Special Functions/EVAP System | This function activates two functions. One function increases or decreases the amount of purge by changing the duty cycle of the purge valve and commanding the vent ON, non-venting. The normal commanded state of both valves is NONE. The system will INCREASE or DECREASE the amount of EVAP purge valve opening by 10 percent increments within a range of 0 percent-100 percent. The second function seals the system after using the purge function to obtain a specific amount of fuel tank pressure (FTP). When activated, the purge valve is commanded to 0 percent and the vent valve is commanded ON, non-venting. Both functions remain in the commanded state until cancelled by the tool or the FTP exceeds -24 mm Hg (-12 in H20). |
| EVAP Service Bay Test | Special Functions/EVAP System | This function activates the Service Bay Test to verify the integrity of the EVAP System. The scan tool initiates the test when the following conditions are met: All the instructions on the scan tool have been completed The engine coolant temperature is less then a specified value No DTCs are set |
| EVAP Vent Solenoid | Special Functions/EVAP System | This function activates the EVAP vent solenoid. The normal commanded state is NONE. When commanded ON, the vent valve switches to non-venting. The system remains in the commanded state unless one of the following conditions occurs: Cancelled by the tool Purge is greater than 0 percent, and the fuel tank pressure (FTP) exceeds -24 mm Hg (-12 in H20) |
| Fuel Pump Relay | Special Functions/Engine Output Controls | This function activates the fuel pump relay. The normal commanded state is NONE. When commanded ON/OFF, the ECM turns the fuel pump relay ON/OFF. If the engine is running and the fuel pump relay is commanded OFF, the engine will stall. The system remains in the commanded state until cancelled by the scan tool. |
| Fuel Economy Test | Special Functions/Fuel System | When the Test is ENABLED the ECM calculates fuel economy based on throttle position, injector pulse width, vehicle speed and engine load. |
| Fuel Trim Reset | Special Functions/Fuel System | This function resets the long term fuel trim values and the rear oxygen sensors learned values. |
| Ignition System | Special Functions/Engine Output Controls | IMPORTANT: The spark tester must be connected to the ignition coil and a good ground before using this function. This function activates the ignition control (IC) circuit for the selected ignition coil for 30 seconds. The scan tool initiates the test when the following conditions are met: The ignition is on with the engine off The vehicle speed is 0 km/h mph Control is not allowed again on the same coil until that ignition coil is allowed to cool for 60 seconds. |
| Intake Manifold Runner Control (IMRC) Solenoid | Special Functions/Engine Output Controls | This function activates the solenoid that supplies vacuum to the IMRC valve located in the intake manifold. The commanded states include NONE, ON and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool. |
| Intake Manifold Tuning (IMT) Valve | Special Functions/Engine Output Controls | This function activates the solenoid that supplies vacuum to the IMT valve located in the intake duct assembly. The commanded states include NONE, ON and OFF. When commanded ON or OFF the system remains in the commanded state until cancelled by the scan tool. |
| Malfunction Indicator Lamp (MIL) | Special Functions/Engine Output Controls/Dash Lamps | This function activates the malfunction indicator lamp (MIL). The commanded states include NONE, ON and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool. |
| Throttle Position | Special Functions/TAC System | This function opens the throttle plate in 25 percent increments. The Scan tool initiates the test when the following conditions are met: The ignition is on with the engine off The vehicle speed is 0 km/h mph The system remains in the commanded state until cancelled by the scan tool. |
| Reset Learned Values | Special Functions/Engine Output Controls | This function resets the long term fuel trim values, the rear oxygen sensors learned values and the crankshaft position variation learn values. |
| IMPORTANT |
|---|
| The spark tester must be connected to the ignition coil and a good ground before using this function. |
Scan Tool Output Controls
Diagnostic Trouble Code (DTC) List
Diagnostic Trouble Code (DTC) List
See also:
• Battery Inspection/Test
• Strategy Based Diagnosis
• Checking Aftermarket Accessories
• Scan Tool Does Not Power Up
• Data Link References
• Body Control System Description and Operation
• Symptoms - Engine Electrical
• Engine Cranks but Does Not Run
• DTC P0030, P0036, P0050, or P0056
• DTC P0172 or P0175
• DTC P0449
• DTC P0461 (3.6L (LY7))
• DTC P0480, P0481, P0691, P0692, P0693, or P0694
• DTC P0500
• DTC P0530, P0532, or P0533
• DTC P0850
• DTC P1629
• DTC P2096 or P2098
• Diagnostic Trouble Code (DTC) List
• Diagnostic System Check - Engine Controls
• Diagnostic Trouble Code (DTC) List