The ECM controls the following:
| • | The fuel system pressure |
| • | The fuel injection timing |
The ECM constantly monitors the information from various sensors. The ECM controls the systems that affect engine performance. The ECM performs the diagnostic function of the system. The ECM can recognize operational conditions, alert the driver through the malfunction indicator lamp (MIL), and store diagnostic trouble codes (DTCs). DTCs identify the faulty areas to aid the technician in making repairs.
The main relay supplies electric power.
Diagnostic Aids
Inspect for the following conditions:
| • | Poor connection at the main relay |
| Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection. |
| • | Damaged harness |
| Inspect the wiring harness for damage, shorts to ground, shorts to battery, and open circuits. If the harness appears to be OK, observe the power supply or data list display on the scan tool while moving connectors and wiring harnesses related to the main relay. A change in the scan tool display will indicate the location of the fault. |
Step | Action | Value | Yes | No |
|---|---|---|---|---|
1 | Is the engine oil within the specified viscosity? | -- | Go to Step 2 | Go to Step 9 |
2 | Is the fuel within the recommended specification? | 30-44 API Gravity | Go to Step 3 | Go to Step 10 |
3 | Bleed the air from the fuel lines by performing the following:
Did the vehicle start and run after priming? | -- | Go to Step 11 | Go to Step 4 |
4 | Inspect the engine compression. Does compression measure more than the specified value for all cylinders? | 2157 kPa (313 psi) | Go to Step 5 | Go to Step 12 |
5 | Inspect the glow plug system operation. Do the glow plugs operate normally? | -- | Go to Step 6 | Go to Step 13 |
6 | Does exhaust brake switch turn OFF? | -- | Go to Step 7 | Go to Step 14 |
7 | Inspect the idling speed control (ISC). Does ISC parameters of the scan tool indicate normal? | -- | System OK | Go to Step 8 |
8 | Inspect the ISC correction items. Do ISC correction items indicate normal operation? | System OK | Go to Step 15 | |
9 | Replace the engine oil. Did you complete the replacement? | -- | Go to Step 16 | -- |
10 | Replace the fuel with the recommended specification. Did you complete the replacement? | 30-44 API Gravity | Go to Step 16 | -- |
11 | Repair the leak in the fuel system. Did you complete the repair? | -- | Go to Step 16 | -- |
12 | Repair/replace the piston ring, the valve stem seal etc. Did you complete the action? | -- | Go to Step 16 | -- |
13 | Repair/replace the glow plug and/or preheating system. Did you complete the action? | -- | Go to Step 16 | -- |
14 | Turn the exhaust brake switch OFF. Did you complete the action? | -- | Go to Step 16 | -- |
15 | Replace the engine control module. Did you complete the replacement? | -- | Go to Step 16 | -- |
16 | Did the engine start and run? | -- | System OK | Go to Step 1 |
