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Fail-safe Chart
=NHEC0040
The ECM enters fail-safe mode, if any of the following malfunctions is detected due to the open or short cir-
cuit. When the ECM enters the fail-safe mode, the MIL illuminates.
DTC No. Detected items Engine operating condition in fail-safe mode
P0100 Mass air flow sensor cir-
cuit
Engine speed will not rise more than 2,400 rpm due to the fuel cut.
P0115 Engine coolant tempera-
ture sensor circuit
Engine coolant temperature will be determined by ECM based on the time after turn-
ing ignition switch “ON” or “START”.
CONSULT-II displays the engine coolant temperature decided by ECM.
Condition
Engine coolant temperature decided
(CONSULT-II display)
Just as ignition switch is turned
ON or Start
40°C (104°F)
More than approx. 4 minutes after
ignition ON or Start
80°C (176°F)
Except as shown above
40 - 80°C (104 - 176°F)
(Depends on the time)
P0120 Throttle position sensor
circuit
Throttle position will be determined based on the injected fuel amount and the
engine speed.
Therefore, acceleration will be poor.
Condition Driving condition
When engine is idling Normal
When accelerating Poor acceleration
P1335 Crankshaft position sensor
(REF) circuit
Compression TDC signal (120° signal) is controlled by camshaft position sensor
(PHASE) signal and crankshaft position sensor (POS) signal. Ignition timing will be
delayed 0° to 2°.
Unable to
access ECM
ECM ECM fail-safe activating condition
The computing function of the ECM was judged to be malfunctioning.
When the fail-safe system activates (i.e., if the ECM detects a malfunction condition
in the CPU of ECM), the MIL on the instrument panel lights to warn the driver.
However it is not possible to access ECM and DTC cannot be confirmed.
Engine control with fail-safe
When ECM fail-safe is operating, fuel injection, ignition timing, fuel pump operation,
IACV-AAC valve operation and cooling fan operation are controlled under certain
limitations.
ECM fail-safe operation
Engine speed
Engine speed will not rise more than 3,000
rpm
Fuel injection Simultaneous multiport fuel injection system
Ignition timing Ignition timing is fixed at the preset valve
Fuel pump
Fuel pump relay is “ON” when engine is running
and “OFF” when engine stalls
IACV-AAC valve Full open
Cooling fans
Cooling fan relay “ON” (High speed condition)
when engine is running, and “OFF” when engine
stalls.
Replace ECM, if ECM fail-safe condition is confirmed.
TROUBLE DIAGNOSIS — GENERAL DESCRIPTION
Fail-safe Chart
EC-122
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