DTC P154D (1.5 L Engine) (2021)

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DTC P154D: Powertrain Control Module (PCM) Low Voltage at Engine Auto Restart

General Description

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

The power supply to each electrical unit temporarily drops due to the drop of the 12 volt battery voltage when the engine is restarted (starter is running) from auto idle stop condition. Normally, the voltage does not fall below the minimum level to operate the electrical unit. But if there is a 12 volt battery performance deterioration or other abnormalities to cause a low voltage, the voltage falls below the minimum level and causes an electrical unit reset. The powertrain control module (PCM) is capable of operating at low voltage compared to other electrical unit; the PCM can be able to monitor the minimum voltage level during engine restart from auto idle stop condition. If the PCM power supply voltage is a specified voltage or less for a specified time, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	10 milliseconds or more
DTC Type	Two drive cycles, MIL off

Enable Conditions

Condition
Starter	ON

Malfunction Threshold

PCM power supply voltage is 5.5 V or less for at least 2 times when the engine is restarted from auto idle stop condition.

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.

12 volt battery performance deterioration
Other than genuine use of 12 volt battery
Poor connections or loose ground terminals between vehicle and 12 volt battery (-) terminal
Poor or loose 12 volt battery (+) terminal cables and connections
Addition of high electric load device

Confirmation Procedure

Operating Condition

Start the engine. Hold the engine speed [ENGINE SPEED] at 3, 000 min -1 (rpm) without load (in P or N) until the radiator fan comes on.
Test-drive the vehicle under the auto idle stop system operating condition, and stop the engine using auto idle stop.
Repeat Driving Pattern steps 1 through 3 at least 2 times.

Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

[ ]: HDS Parameter

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 and the freeze data are stored. The MIL does not come on.

Conditions for clearing the DTC

The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.