Circuit Description
The serial data communications system allows various modules to communicate and share information with each other. This reduces the vehicle electrical wiring and provides for the transmission and reception of module signals over a single wire. If the BCM cannot respond to the PCM, DTC U1064 is stored.
Conditions for Setting the DTC
The PCM cannot communicate with the body control module (BCM) for 15 seconds after having previously established communications with the BCM for that ignition cycle.
Action Taken When the DTC Sets
| • | The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Failure Records buffer. |
| • | A history DTC is stored in the PCM and IPC. |
Conditions for Clearing the DTC
| • | IPC DTC U1064 status changes from current to history when the BCM receives the vehicle security powertrain status message from the PCM. |
| • | A history DTC will clear in the PCM after 40 consecutive warm up cycles without a malfunction. |
| • | A scan tool can clear the DTC. |
Diagnostic Aids
| • | An intermittent problem may be caused by the following conditions: |
| - | Poor electrical connection |
| - | Rubbed through wire insulation |
| - | A wire that is broken inside the wire insulation |
| • | 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 electrical connectors |
| - | Damaged terminals |
| - | A poor terminal to wire connection |
| • | Install an additional ground wire from the IPC to the negative side of the battery if electrical interference is suspected. |
Test Description
The numbers below refer to the step numbers 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 in the scan tool for later reference.
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A scan tool that cannot display PCM data indicates that a short, or open may exist on the serial data circuit. Refer to Scan Tool Does Not Communicate with Components .
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An intermittent short on the serial data circuit could cause this DTC to set. When the malfunction is present, the scan tool will lose communication with the PCM and the body control module (BCM). Check for chaffed wiring or a malfunctioning BCM.
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The DTC is intermittent when a scan tool can communicate with the PCM and the BCM. DTCs within the BCM, the IPC, or the EBCM may lead to a possible cause of the intermittent problem.
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If the serial data loss occurred after a good theft password has been received, the PCM will allow the vehicle to be started on following attempts. After making the necessary repairs to the vehicle, the PCM must be reprogrammed and the password learn procedure and the crankshaft position system variation procedures must be completed to allow the theft system to operate properly. Refer to Crankshaft Position System Variation Learn in Engine Controls - 2.4L or Crankshaft Position System Variation Learn in Engine Controls -3.1L for the reprogramming procedures.
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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 checks and information.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 2.4L or Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 3.1L | |||||||
Can the scan tool display data from the PCM? | -- | Go to Step 3 | ||||||||
3 | Can the scan tool display body control module (BCM) data? | -- | Go to Step 4 | Go to Body Control Module System Check in Body Control Systems | ||||||
Was a repair necessary? | -- | Go to Step 6 | Go to Step 5 | |||||||
Is the action complete? | -- | Go to Step 6 | -- | |||||||
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 7 | Go to Step 2 | |||||||
Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 2.4L or Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 3.1L |
