Toyota training course t852 engine control systems sec03

Technician Handbook
874 Engine Control Systems II

Comprehensive
Components
Monitor Overview

The comprehensive components (composition parts) monitor is
used to monitor individual components. This monitor checks
component circuits for opens, shorts, or performance issues. If the
component affects vehicle emissions but is not part of the other
monitored systems, it is a comprehensive component. The
comprehensive components monitor is a continuous monitor.
Many comprehensive components have two types of DTCs. An
open, a short, or no response is a one trip DTC. A performance
problem is usually a two trip DTC.
An example of a comprehensive component is the MAF sensor. If
the ECM measures high or low voltage at the MAF sensor circuit
when enabling conditions have been met, it will set an open or short
DTC. During normal operation, the MAF signal is roughly
proportional to engine load. If this varies greatly, the ECM will set a
signal performance DTC.
Many comprehensive components exist on vehicles. Most open,
short, or performance DTCs are the result of the comprehensive
component monitor.

NOTE

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The best source of the DTC setting parameter information is the

Repair Manual specific to the vehicle. Some parameters may not be
outlined but should be assumed, i.e. engine at operating
temperature. Carefully study the information to determine what must
occur before a DTC will be recorded and how to diagnose the issue.
The DTC may be the result of an out-of-spec system monitor, not a
component that has failed, and may be remedied with a new ECM
calibration or upgrade. Check for applicable Service Bulletins (SB)
when diagnosing a malfunction detected by the comprehensive
component monitor.
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Technician Handbook
874 Engine Control Systems II

Mass Air Flow (MAF)
Sensor Circuit

There are two DTCs directly applicable to the MAF circuit. DTC P0100
is set when an open or short occurs in the MAF circuit. It is a one trip
DTC and has Fail-Safe strategy. The Fail-Safe strategy fixes the
ignition timing and the on time of the fuel injectors according to engine
conditions.
DTC P0101 has three different conditions to detect MAF sensor/circuit
failure. ECM is comparing the MAF signal against the expected MAF
signal when compared to throttle position and engine speed.
The information in the image is from the P0100 and P0101 DTC
troubleshooting sections of the Repair Manual.

Comprehensive Components

Monitor Diagnosis

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Many comprehensive components exist on vehicles. Most open, short,
or performance DTCs are the result of the comprehensive component
monitor. When trying to determine the cause of a circuit open, short, or
performance issue, visually inspect the suspect component. Check the
Freeze Frame Data (FFD) and duplicate the conditions. Use the
Technical Information System (TIS) for Repair Manual (RM) and
Electrical Wiring Diagram (EWD) information and look for applicable
Service Bulletins (SB).

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Technician Handbook
874 Engine Control Systems II

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