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5B.8
Section 5B
EFI Fuel System
If the resistance values in steps 3, 4, and 5 are
within specifications, go to step 6.
If the resistance values are not within
specifications, or a momentary short or open
circuit was detected during rotation (step 4), the
TPS needs to be replaced, go to step 7.
6. Check the TPS circuits (input, ground) between
the TPS plug and the main harness connector for
continuity, damage, etc. See chart on pages
5B.28, 5B.31, or 5B.32.
“35 Pin” (MA 1.7) Metal-Cased ECU: Pin
Circuits #12 and #27.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin
Circuits #8 and #4.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin
Circuits #8 and #4.
a. Repair or replace as required.
b. Turn the idle speed screw back in to its
original setting.
c. Reconnect connector plugs, start engine and
retest system operation.
7. Remove the two mounting screws from the TPS.
Save the screws for reuse. Remove and discard
the faulty TPS. Install the replacement TPS and
secure with the original mounting screws.
a. Reconnect both connector plugs.
b. Perform the appropriate “TPS Initialization
Procedure” integrating the new sensor to the
ECU.
TPS Initialization Procedure
For “35 Pin” (MA 1.7) Metal-Cased ECU and
“24 Pin” (MSE 1.0) Plastic-Cased ECU only
1. Check that the basic engine, all sensors, fuel, fuel
pressure, and battery are good and functionally
within specifications.
Important!
2. Remove/disconnect ALL external loads from
engine (belts, pumps, electric PTO clutch,
alternator, rectifier-regulator, etc.).
3. Start the engine and allow it to warm up for 5-10
minutes, so oil temperature is above 55°C
(130°F).
4. Move the throttle control to the idle position and
allow engine to stabilize for a minimum of one
minute.
5. Install a heavy rubber band around the throttle
lever and the manifold boss, to firmly hold the
throttle against the idle stop. On some EFI
engines there is a dampening spring on the end
of the idle speed screw. The dampening spring (if
used) should be fully compressed and the tab on
the throttle lever in direct contact with the speed
screw. Adjust the idle speed to 1500 RPM, using
a tachometer.
6. Shut off engine.
7. Locate the service connector plug in the wiring
harness.
“35 Pin” (MA 1.7) Metal-Cased ECU: Connect a
jumper wire from the TPS initialization pin #8
(gray wire) to the ground pin (black wire), or use
jumper plug (SPX Part No. KO3217-7, with red
jumper wire). See Figure 5B-8.
Throttle
Position
Closed
Closed
Full
Full
Any
Between
Terminals
2 & 3
1 & 3
2 & 3
1 & 3
1 & 2
Resistance
Value (Ω)
800-1200
1800-3000
1800-3000
800-1200
1600-2500
Continuity
Yes
Yes
Yes
Yes
Yes
4. Leave the leads connected to the pin terminals as
described in step 3. Rotate the throttle shaft
slowly counterclockwise to the full throttle
position. Monitor the dial during rotation for
indication of any momentary short or open
circuits. Note the resistance at the full throttle
position. It should be 1800-3000
ΩΩ
ΩΩ
Ω.
5. Disconnect the main wiring harness connector
from the TPS, leaving the TPS assembled to the
manifold. Refer to the chart below and perform
the resistance checks indicated between the
terminals in the TPS switch, with the throttle in the
positions specified.