Circuit Description
The Powertrain Control Module (PCM) has four fuel injector driver circuits, each of which controls a fuel injector. The PCM monitors the current in each driver circuit and is able to control the driver circuit. The current through each driver can rise to a peak of 2 amps in order to quickly open the fuel injectors. The current can reduce to 1/2 amp to hold the fuel injectors open. This is called peak and hold. If the current cannot reach a 2-amp peak, a DTC is set. This DTC is also set if a fuel injector driver is shorted to voltage.
Conditions for Setting the DTC
| • | Injector current is less than 4 amps. |
| • | Battery voltage is more than 9 volts. |
| • | Above conditions met for 5 seconds. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates. |
| • | The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage will cause a DTC P0200 to set and will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which cylinder is inoperative.
Long term and short term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Use Fuel Injector Solenoid Coil Test (ECT Within 10C-35C (50F-95F) to check for malfunctioning injectors.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check 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 determines if DTC P0200 is the result of a hard malfunction or an intermittent condition.
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Test the harness wiring and for PCM control of the fuel injectors using test light J 34780-2. If the tests light blinks, the PCM and wiring to the fuel injectors are OK. Fuel Injector Solenoid Coil Test (ECT Within 10C-35C (50F-95F) will check if the fuel injectors are malfunctioning.
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Whether the test light was ON steady or OFF while cranking the engine narrows the possible malfunctions down to just a few.
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Because the test light was ON steady, voltage to the fuel injector is OK, but the fuel injector driver circuit is grounded at all times. This step determines if the circuitry is shorted to ground or the PCM is malfunctioning.
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Replacement PCMs must be reprogrammed. Refer to the latest Isuzu Technical Communication System (ITCS) information for programming procedures.
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Determines if voltage is available to the fuel injector. Voltage is supplied through the fuel pump relay so the engine must be cranked to see voltage at the fuel injector.
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This step determines if the fuel injector driver circuit is open or shorted to voltage or if the PCM is malfunctioning.
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Since voltage is supplied to the injector on a single circuit before the injector harness, the malfunction could only be a poor connection or open in the injector harness. An open before the harness would result in a Cranks But Won't Run complaint.
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Check the injector electrical connector, the injector harness connector and the PCM for poor connections or corroded terminals.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
2 | Will the engine start and continue to run? | -- | ||
Does DTC P0200 reset? | -- | |||
4 |
Does P0200 Reset? | -- | ||
Does the fuel injector test light blink on all test? | -- | |||
Note whether the fuel injector test light was OFF or ON steady in step 5 for the injector connector that did not blink. Was the fuel injector test light ON steady while cranking the engine? | -- | |||
Does the test light illuminate? | -- | |||
8 | Check for a short to ground in the injector driver circuit and repair as necessary. Was a repair necessary? | -- | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
Does the test light illuminate while cranking? | -- | |||
Is the test light OFF while cranking? | -- | |||
Repair the open in the ignition feed circuit in the fuel injector harness. Is the action complete? | -- | -- | ||
Check the fuel injector driver circuit for an open or malfunctioning connection. Was a problem found? | -- | |||
14 | Repair the short to voltage in the fuel injector driver circuit. Is the action complete? | -- | -- | |
15 | Repair the open or malfunctioning connection in the fuel injector driver circuit. Is the action complete? | -- | -- | |
16 |
Does the scan tool indicate that this diagnostic has ran and passed? | -- | ||
17 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
