Circuit Description
Output Driver Modules (ODMs) are used by the PCM to turn on many of the current-driven devices that are needed to control various engine and Transaxle functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM is commanding ON. Unlike the Quad Driver Modules (QDMs) used in prior model years, ODMs have the capability of diagnosing each output circuit individually. DTC P1643 set indicates an improper voltage level has been detected on ODM A output 3, which controls the Fuel Pump PWM signal to the fuel pump control module.
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | An improper voltage level has been detected on ODM A output 3 (the Fuel Pump PWM control circuit). |
| • | The above conditions are present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM will not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM. 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. |
| • | If the harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a digital multimeter connected between the Fuel Pump Speed Control PWM circuit and ground at the PCM harness connector while moving connectors and wiring harnesses related to the Fuel Pump Control Module. A change in voltage will indicate the location of the malfunction. |
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
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Normally, ignition feed voltage present on the output driver circuit with the PCM disconnected and the ignition turned ON.
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Checks for a shorted component or a short to B+ on the output driver circuit. Either condition would result in a measured current of over 0.5 amps.
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Checks for a faulty Fuel Pump Speed Control Relay.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic System Check performed? | -- | Go to the Powertrain OBD System Check | |
2 |
Important: If the vehicle cranks but will not run, refer to Engine Cranks But Will Not Run.
Is voltage near the specified value? | B+ | ||
3 |
Does the current reading remain within the specified values? | 0.5 - 1.5 Amp | ||
4 |
Is the current reading less than the specified value? | 0.5 Amp | ||
5 | Locate and repair short to voltage in the Fuel Pump Speed Control driver circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
6 |
Is the test light ON? | -- | ||
7 | Locate and repair open in the fuel pump speed control driver circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
8 | Locate and repair short to ground in the fuel pump speed control driver circuit. Refer to Repair Procedure in Electrical Diagnosis. Is action complete? | -- | -- | |
9 |
Was a problem found? | -- | ||
10 | Replace the Fuel Pump Speed Control relay. Is action complete? | -- | -- | |
11 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Is action complete? | -- | -- | |
12 |
Note test result; does scan tool indicate DTC P1643 failed this ign? | -- | System OK |
