633 / 4910
Q501 4 Cylinder MT Application
DTC Troubleshooting Data
Version: 0.1
Date: 21-Sep-2018
Prepared By: Mithi Prasad, Sarang Kulkarni, Manish Gupta
Checked By: Yogesh Jadhav
Approved By: Satish Kumar P
Page: 601 of 1052
Copyright ©
TATA MOTORS Ltd.
This document must not be used in any way, such as copying and redistributing to third parties, without the consent of author.
P00BC-21: Mass or Volume Air Flow “A” Circuit Range / Performance – Air Flow Too Low – Air mass meter
sensitivity drift (signal below lower limit)
Overview:
DTC Description (User Friendly)
Air mass meter sensitivity drift (signal below lower limit)
ECU Pin Number
K086
Customer Symptom
MIL ON, Engine Power Loss
Fault Effects (On Vehicle)
Reduced Torque mode activated.
Lamp Status (If Any)
MIL ON.
MIL OFF: After 3 warm up Cycles (Drive Cycle with coolant
temperature increase by 22 degrees) or Clear DTC Command
with fault condition no more present.
Fault Detection Condition (Root cause)
When the air flow meter measures an air flow rate lower than
the internal ECU calculated mass by gas equation of at least
20%
Normal Operating Condition
Air Mass flow sensor input is in between the upper and lower
limits
Probable Trouble Area
1. High resistance in the fused main relay supply circuit to
MAF sensor
2. High resistance in the MAF sensor signal (Air Flow /
Temperature) circuit.
3. High resistance in the MAF sensor ground circuit
4. Intake Air system leak / restriction
5. EGR System leak
6. MAF sensor
7. EMS ECU
Healing Condition
Rectify the error
Clear through diagnostic tool
Ignition OFF & ON
Component Details:
The operating principle is based on the heating of a diaphragm (sensitive element
containing two resistances upstream and downstream of the support) in a by-pass duct through which the engine intake
air flows. The hot film membrane is maintained at constant temperature (about 120 °C higher than the incoming air
temperature) by the specific heating resistance controlled by the management electronics. The mass of air passing
through the by-pass duct, giving off heat to the membrane, thermally unbalances the two resistances to an extent directly
proportional to the mass of the incoming fluid, an imbalance that is translated through the control circuit into a resistance
variation, electronically processed and translated into a frequency value to be sent to the engine management control unit.
The imbalance in the resistance value also makes it possible to determine the direction of the column of air. As far as the
air temperature information is concerned, it is sent to the engine management control unit via a dedicated pin in the form
of a duty cycle signal (rectangular wave). The value of the duty is proportional to the value of the temperature.
Preliminary Checks:
1. Check whether the customer voice / view about the issue is matching with the fault effects mentioned in above
Table. If yes, go ahead with next steps. If not, check for other DTC’s presence.
2. Check whether other customers report similar complaints earlier. If yes, perform the preliminary checks with
respect to earlier issue closure.
3. Check for any other faults presence related to ECU Internal power supplies; Follow rectification process for those
faults, before proceeding further.