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5B.26
Section 5B
EFI Fuel System
Electrical System
The EFI system is a 12 VDC negative ground system,
designed to operate down to a minimum of 7.0 volts.
If system voltage drops below this level, the operation
of voltage sensitive components such as the ECU, fuel
pump, and injectors will be intermittent or disrupted,
causing erratic operation or hard starting. A fully
charged, 12 volt battery with a minimum of 350 cold
cranking amps is important in maintaining steady and
reliable system operation. Battery condition and state
of charge should always be checked first when
troubleshooting an operational problem.
Keep in mind that EFI-related problems are more
often caused by the wiring harness or connections
than by the EFI components. Even small amounts of
corrosion or oxidation on the terminals can interfere
with the milliamp currents used in system operation.
Cleaning the connectors and grounds will solve
problems in many cases. In an emergency situation,
simply disconnecting and reconnecting the connectors
may clean up the contacts enough to restore operation,
at least temporarily.
If a fault code indicates a problem with an electrical
component, disconnect the ECU connector and test for
continuity between the component connector
terminals and the corresponding terminals in the ECU
connector using an ohmmeter. Little or no resistance
should be measured, indicating that the wiring of that
particular circuit is OK. An illustrated listing of
numerical terminal locations, for each style of ECU
connector is provided on pages 5B.26 and 5B.29.
NOTE: When performing voltage or continuity tests,
avoid putting excessive pressure on or
against the connector pins. Flat pin probes
are recommended for testing to avoid
spreading or bending the terminals.
“24 Pin” (MSE 1.0) Plastic-Cased ECU Systems
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Function
1
Permanent Battery Voltage
Switched Ignition Voltage
Safety Switch
Throttle Position Sensor (TPS) and Temperature Sensor Ground
Not Used
Oil Temperature Sensor Input
Not Used
Throttle Position Sensor (TPS) Input
Speed Sensor Input
Speed Sensor Ground
Oxygen Sensor Input
Not Used (Oxygen Sensor Ground if needed)
Diagnostic Line
Throttle Position Supply Voltage
Battery Ground
Injector 1 Output
Injector 2 Output
Main Relay Output
Malfunction Indicator Light (MIL)
Not Used (Tach Output if needed)
Not Used
Ignition Coil #1 Output
Ignition Coil #2 Output
TPS Initialization Terminal
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24