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. |
Under this injection system, the main relay is activated by the key ON signal, so that all the systems including CPU are powered by the main relay.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Inspect the starting/charging system. Did the charging/starting system test normal? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Electrical in Engine Electrical | ||||||||
2 |
Does the fuel pressure measure more than the specified value? | 10 psi | Go to Step 3 | Go to Step 21 | ||||||||
3 |
Does the voltage measure more than the specified value? | 10 V | Go to Step 4 | Go to Step 19 | ||||||||
4 |
Does the voltage measure more than the specified value? | 10 V | Go to Step 6 | Go to Step 5 | ||||||||
5 |
Did you find and correct the condition? | -- | Go to Step 28 | Go to Step 6 | ||||||||
6 |
Does the resistance measure less than the specified value? | 1 ohms | Go to Step 7 | Go to Step 20 | ||||||||
7 | Measure the resistance of the ECM case grounds. Does the resistance measure less than the specified value? | 1 ohms | Go to Step 8 | Go to Step 20 | ||||||||
8 |
Does the voltage measure more than the specified value? | 10 V | Go to Step 9 | Go to Step 19 | ||||||||
9 |
Important: If radio noise has worsened in addition to the system abnormality, inspect the case grounds of the ECM, as well as the following circuits.
Did you find and correct the condition? | -- | Go to Step 28 | Go to Step 11 | ||||||||
10 | Is the engine oil the proper viscosity and level? | -- | Go to Step 11 | Go to Step 23 | ||||||||
11 | Is the fuel within the recommended specification? | 30-44 API Gravity | Go to Step 12 | Go to Step 24 | ||||||||
12 | Bleed the air from the fuel line. Did you complete the action? | -- | Go to Step 13 | -- | ||||||||
13 | Inspect the engine compression. Does the engine compression measure more than the specified value for all cylinders? | 2157 kPa (313 psi) | Go to Step 14 | Go to Step 25 | ||||||||
14 | Inspect the glow plug system operation. Do the glow plugs operate normally? | -- | Go to Step 15 | Go to Step 26 | ||||||||
15 | Inspect the injection timing with a scan tool. Are the injection timing parameters normal? | -- | Go to Step 16 | |||||||||
16 | With fuel pressure not supplied, is the PC sensor output normal? | -- | Go to Step 17 | Go to DTC P1298 | ||||||||
17 | Are the PC valves operating normally? | -- | Go to Step 18 | |||||||||
18 | Does the supply pump operate normally? | -- | Go to Step 28 | Go to Step 27 | ||||||||
19 | Repair the harness. Did you complete the repair? | -- | Go to Step 28 | -- | ||||||||
20 | Repair the circuit or connection. Did you complete the repair? | -- | Go to Step 28 | -- | ||||||||
21 | Repair the fuel supply line leak or restriction. Did you complete the repair? | Go to Step 28 | ||||||||||
22 | Replace the ECM. Did you complete the replacement? | -- | Go to Step 28 | -- | ||||||||
23 | Replace the engine oil. Did you complete the replacement? | -- | Go to Step 28 | -- | ||||||||
24 | Replace the fuel with the recommended specification. Did you complete the replacement? | 30-44 API Gravity | Go to Step 28 | -- | ||||||||
25 | Repair the engine condition. Did you complete the repair? | -- | Go to Step 28 | -- | ||||||||
26 | Repair the glow plug system. Did you complete the repair? | -- | Go to Step 28 | -- | ||||||||
27 | Replace the supply pump assembly. Did you complete the replacement? | -- | Go to Step 28 | -- | ||||||||
28 | Does the engine start and run? | -- | System OK | Go to Step 1 |
