DTC Advanced Diagnostics: P0A94 (2.0L 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	Minimum	Maximum
12 volt battery voltage [Battery]	10.5 V	-
Vehicle	ON mode

[ ]: HDS Parameter

Malfunction Threshold

The PCM receives a DC-DC converter failure information via the LIN line for at least 5 seconds.

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 GND 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.