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5B.10
Section 5B
EFI Fuel System
Figure 5B-10. Engine (Oil) Temperature Sensor.
General
The engine (oil) temperature sensor (Figure 5B-10) is
used by the system to help determine fuel
requirements for starting, (a cold engine needs more
fuel than one at or near operating temperature).
Mounted in the oil filter adapter housing, it has a
temperature-sensitive resistor that extends into the oil
flow. The resistance changes with oil temperature,
altering the voltage sent to the ECU. Using a table
stored in its memory, the ECU correlates the voltage
drop to a specific temperature. Using the fuel delivery
“maps”, the ECU then knows how much fuel is
required for starting at that temperature.
Service
The temperature sensor is a sealed, non-serviceable
assembly. A faulty sensor must be replaced. If a blink
code indicates a problem with the temperature sensor,
it can be tested as follows.
1. Remove the oil temperature sensor from the
adapter housing and cap or block the adapter
hole.
2. Wipe sensor clean and allow it to reach room
temperature (20°C, 68°F).
3. Unplug the main harness connector from the
ECU.
4. With the sensor connected, check the oil
temperature sensor circuit resistance. The value
should be 2375-2625
ΩΩ
ΩΩ
Ω. See chart on pages
5B.28, 5B.31, or 5B.32.
“35 Pin” (MA 1.7) Metal-Cased ECU: Check
between the #14 and #27 pin terminals.
5. Remove the jumper wire or plug from the service
connector plug in wiring harness.
6. Run the engine at full throttle (above 3000 RPM),
to warm up the engine and initiate O
2
sensor
function in “closed-loop” operation.
7. Watch the “MIL”. When the light starts blinking
rapidly, (5 blinks per second), move the throttle
lever to the low idle speed position. Check and
adjust the idle speed to 1500 RPM, using a
tachometer. The lamp should continue to blink
rapidly for another 30 seconds before switching to
a slow blink.
8. When the “MIL” blinks slowly, do not do anything
but wait until the “MIL” shuts off. This indicates
that this procedure has been completed
successfully.
9. Shut off the engine.
If the learn procedure was successfully
completed, the external loads removed/
disconnected in Step 2 may be reconnected.
If the procedure was unsuccessful see Steps a.
and b. following.
a. If during this procedure, the “MIL” goes back
into blinking 4 consecutive blinks every 2
seconds, the engine and O
2
sensor have
cooled down and out of “closed-loop”
operation, prohibiting the learning from
occurring. Repeat Steps 6-9.
b. If during the procedure with the engine
running, the “MIL” stays “on” continuously, for
more than 15 seconds, turn off the ignition.
Then initiate the fault code sequence, by doing
three consecutive key-on/key-off cycles
leaving the key “on” in the last sequence,
(each key-on/key-off sequence must be less
than 2.5 seconds long). The fault detected
must be corrected before the “auto-learn”
function can be re-initiated. The PC-based
diagnostic tool and software may be used to
read out the fault code and assist with the
troubleshooting and repair.
Engine (Oil) Temperature Sensor