Porsche H040 Data PID Use in Diagnosing Air Mass Issues

Porsche uses a data value referred to as H040 to measure deviations between the mass air flow before and after the throttle plate. This value is used on engines equipped with a mass air flow sensor as well as a MAP sensor to determine throttle angle set point value.

The value is displayed as a percentage with a range of +49.99 to -49.99.

Common fault codes like P1070 and P1071 may be stored.

P0068 - MAF implausible

P1070 - Mass air flow at idle speed implausible - low slow deviation

P1071 - Mass air flow at idle speed implausible - high fast deviation)

If you have a vacuum leak, for example a faulty purge solenoid, leaking intake manifold or a faulty crankcase breather valve (AOS) the deviation will be in the positive direction.

This is because of additional air mass in the intake that did not pass through the throttle plate. The DME sees too much air for the current throttle angle.

If you have increased throttle angle and less than expected air mass, for example from a dirty throttle plate or leaking throttle plate shaft, the deviation will be in the negative direction.

This is because the current air mass in the intake manifold is too little for the current throttle angle.

Keep in mind, this is not a fuel trim control, rather a calculation of the total deviation using mass air flow, purge activation and fuel trim correction factors compared to throttle angle.

If you have a deviation, use the information here to inform your fuel trim testing.

Thanks for watching and check out the video description for bonus information on H040 as well as throttle cleaning and adaptation.

H040: Correction factor, mass air flow
Meaning: The mass air flow (kg/h) is calculated from the pressure ahead of the throttle valve (P.amb) + pressure behind the throttle valve (PAT model) + throttle valve angle. The calculated mass air flow is compared with the mass air flow measured by the MAF sensor (mass air flow + tank vent valve + correction factors). The deviation is displayed as a percentage (max. 49.99). Limit values differ according to the load range. Deviation
is in the high positive range if adaptation was performed while the engine was hot.