Service manual

90-898303

3-5

EFI Electrical Components

1995-2001 3.0L

SENSOR INTERACTION WITH ECM

The ECM relies on sensor feedback to provide proper fuel rates and timing

advance for optimum engine performance under all conditions.

Should a sensor fail, the ECM will try to compensate for lack of sensor

information by providing predetermined fuel rates and timing advance for

average conditions.

Therefore, a change in engine performance may not be readily noticeable.

However, a sensor failure will result in the ECM activating a warning horn to

alert the operator.

The Fuel ECM uses a pulse from the stator feed into #1 CDM to locate

crankshaft position, then uses the gray tachometer signal wire (RPM) from the

ignition ECM to determine when to fire the injectors in pairs.

IMPORTANT: DO NOT run engine for extended periods of time with

sensors disconnected or bypassed (shorted). Serious engine damage

may result.

AIR TEMPERATURE SENSOR

The air temperature sensor transmits manifold air temperature, through full

RPM range, to the EFI ECM. As air temperature increases “sensor” resistance

decreases causing the ECM to decrease fuel flow (leaner mixture).

NOTE: A warning horn will sound if the sensor fails or is disconnected on

1996 models, only.

The air temperature sensor circuit can be tested using a volt/ohm meter.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

The MAP sensor is mounted on the vapor separator. This sensor monitors

changes in manifold absolute pressure and is connected to the intake

manifold by a vacuum hose. The MAP sensor functions through the full RPM

range and is continually signaling induction manifold pressure readings to the

EFI ECM. The EFI ECM determines fuel flow as signals are received. Drawing

a vacuum on the MAP sensor hose will create a lean fuel condition altering

engine operation. If no change occurs when drawing vacuum, MAP sensor is

not functioning properly.

NOTE: A warning horn will sound if sensor fails or is disconnected on 1996

models, only. The engine may, however, run rough at idle if the sensor is

inoperative on all models.

ENGINE HEAD TEMPERATURE SENSOR

This sensor provides the EFI ECM with signals related to engine temperature

to determine level of fuel enrichment during engine warm-up. The EFI ECM

receives information at all engine temperatures but stops fuel enrichment at

an engine temperature of 110° F (43° C).

Notes

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