Code No. P1238: Air Flow Sensor Trustful For Torque Monitoring

FUNCTION

Compare the actual measurement of volumetric efficiency by an air flow sensor signal with volumetric efficiency estimated from a throttle position sensor (main and sub) signal.

TROUBLE JUDGMENT

Check Conditions

Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is more than 0 %. Or, the volumetric efficiency is less than 60 %.
Engine speed is more than 750 r/min.

Judgement Criterion

Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is more than 35 %.

Check Conditions

Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is more than 0 %. Or, the volumetric efficiency is less than 60 %.
Engine speed is more than 750 r/min.

Judgement Criterion

Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is more than 35 %.

FAIL-SAFE AND BACKUP FUNCTION

Throttle opening degree position is in default position.

PROBABLE CAUSES

Failed air flow sensor
Harness damage in air flow sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q. Is any other diagnosis code than P1238 set?

	Inspection chart for diagnosis code (Refer to ).

	Go to Step 2.

STEP 2. M.U.T.-III data list

Data list reference table (Refer to ).

Item 10: Air flow sensor

Q. Is the check result normal?

	Replace the engine-ECU.

	Check air flow sensor system. Check code No. P0102: air flow sensor circuit low input (Refer to . Check code No. P0103: air flow sensor circuit high input (Refer to ).