1A-12 Engine General Information and Diagnosis:
Fail-Safe System Description
Z9J0111101005
The fail-safe system is closely related to the self-diagnostic system.
When an abnormality occurs in a sensor signal, the ECM ignores the out-of-range signal and assumes a pre-
programmed value for the failed sensors.
This allows the engine to continue running under the fail-safe condition.
Pre-Programmed Value for Fail-Safe System
NOTE
There is no back-up system for the ECM itself. The engine will stop if it has failed.
Neutral switch
• While the shift sensor outputs a forward or reverse signal, the ECM
receives a neutral signal from the neutral switch.
Rectifier/Regulator
(Over-charging)
• Receiving 16 volts or higher signal.
Oil pressure switch
• While the engine is stopped and the ignition switch is on, the ECM receives
an “off” signal from the oil pressure switch.
Trim sensor • Receiving an out of range “0.2 – 4.8 V” signal.
Failed Item Condition
Failed Item Pre-Programmed Value
MAP sensor 1 • 150 – 758 mmHg / (5.9 – 30 inHg.)
(The value will change according to the current engine speed.)
Air intake system • The control is executed with the maximum engine speed of 2 000 r/min.
Cylinder temp. sensor 60 °C (140 °F)
IAT sensor 45 °C (113 °F)
Exhaust manifold temp. sensor 60 °C (140 °F)
Throttle position sensor • The control is executed with the throttle opening at 5 degrees.
Shift position sensor • The shift position (Fwd / Neu / Rev) is detected with the neutral switch signal.
Trim sensor • The control is continued with fixed sensor output as 3.5 V.
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