DTC Advanced Diagnostics: P0A94 (3.0L Engine)

DTC P0A94: DC-DC Converter Performance Problem

General Description

Courtesy of HONDA, U.S.A., INC.

The auto idle stop system equipped vehicle uses the DC-DC converter to prevent electronic accessory reset due to the 12 volt battery voltage lowering when recovering (starter motor running) from auto idle stop condition. The DC-DC converter is connected with DC_STS line for the powertrain control module (PCM) to send a voltage boost request and the local interconnect network (LIN) line for sending a diagnostic result to the PCM. When the self-diagnostic circuit in the DC-DC converter detects a failure, it is noticed to the PCM via the LIN line. If the PCM receives a DC-DC converter failure information for a set time, the PCM detects a DC-DC converter performance problem and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	5 seconds or more
DTC Type	Two drive cycles, MIL off

Enable Conditions

Condition
Vehicle	ON mode
Other	LIN communication is OK

Malfunction Threshold

The PCM receives any of the following information from the DC-DC converter for at least 5 seconds.

Internal circuit failure
Abnormal boosting control
Abnormal load voltage
Abnormal input voltage
Over load current

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

DC-DC converter +B_VST1 line open
DC-DC converter +B_VST1 line short
DC-DC converter +B_VST2 line open
DC-DC converter +B_VST2 line short
DC-DC converter DC_STS line short
DC-DC converter IG1_ACG line open
DC-DC converter +B_DC1_OUT1 line short
DC-DC converter +B_DC1_OUT2 line short
DC-DC converter V6_DC_PGND line open
Electrical unit failure
DC-DC converter failure
PCM internal circuit failure

Diagnosis Details

Conditions for setting the DTC

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, a Confirmed DTC, the freeze data, and the on-board snapshot are stored. The MIL does not come on.

Conditions for clearing the DTC

The Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.