Circuit Description
The engine control module (ECM) monitors the ignition voltage on the ignition feed circuit to terminal K18 at the ECM. A system voltage DTC will set whenever the voltage is below a calibrated value.
Conditions for Setting the DTC
| • | The system voltage is less than 11 volts. |
| • | The engine is running. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
If the DTC sets when an accessory is operated, inspect for a poor connection or excessive current draw.
Any circuitry that is suspected as causing the intermittent complaint should be thoroughly inspected for the following conditions:
| • | Backed-out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed |
| • | Damaged terminals |
| • | Poor terminal-to-wiring connections |
| • | Physical damage to the wiring harness |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
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This step inspects if the generator is malfunctioning under load conditions.
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The step inspects the ignition feed circuit for excessive resistance. An open circuit will cause a not start condition.
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The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.
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If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional inspections and information.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Perform the Diagnostic System Check - Engine Controls. Was the check performed? | -- | Go to Step 2 | ||
Is the ignition voltage less than the specified value? | 10 V | Go to Step 3 | Go to Step 8 | |
3 | With the engine still running at 1,400 RPM, use a voltmeter to measure the battery voltage at the battery. Is the battery voltage greater than the specified value? | 12 V | Go to Step 4 | Go to Diagnostic Aids |
Is the ignition voltage greater than the specified value? | 10 V | Go to Step 5 | Go to Step 6 | |
5 | Inspect for a malfunctioning connector at the ECM harness terminals and repair as needed. Is the repair complete? | -- | Go to Step 8 | Go to Step 7 |
6 | Repair the poor connection, high resistance, in the ignition feed circuit. Is the repair complete? | -- | Go to Step 8 | -- |
7 |
Is the repair complete? | -- | Go to Step 8 | -- |
8 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 9 | Go to Step 2 |
9 | Are any DTCs displayed that have not been diagnosed? | -- | System OK |
