FBC System - Voltmeter Check Procedure

84mitsubishi02

NO. STB-84-14-012

DATE June, 1984

MODEL 1984 2.0L Cordia/Tredia

SUBJECT:

1984 FBC SYSTEM VOLTMETER CHECK PROCEDURE
USE OF VOLTMETER TO TEST FBC SYSTEM

The FBC electronic systems on 1984 Cordia/Tredia 2.0L models can be checked using your digital multimeter or any high-impedance voltmeter. This method is useful when you want to check the FBC system without unplugging the connectors, or when an ECI checker is not available.

Figure 1:

VOLTMETER PROBES AND CONNECTIONS

To perform the FBC system tests, you will measure voltages right at the computer which is on the right cowl kick panel. Make up a set of thin probes (paper clips work fine) to attach to your voltmeter and insert into the tops of the connectors on the computer as shown in Figure 1. You don't have to unplug the connectors.

CAUTION: Short-circuiting the positive (+) probe between a connector terminal and ground could damage the vehicle wiring, the sensor, the ECU, or all three. Use care to avoid it! Insulate the exposed part of the probe with electrical tape as a precaution.

Figure 2:

TEST PROCEDURE

1. Remove the cowl side panel to reach the computer terminal connectors.

2. Attach the black (-) lead of the voltmeter to a good ground, such as the computer box.

3. Refer to the 1984 FBC System Voltmeter Check Chart I (see page 3). Note the connector terminal callouts in the right column. Insert the positive probe into each connector terminal in turn. Switch the ignition from OFF to ON, and compare the voltage with that shown in the chart. For example, when the probe is on terminal A13, the voltmeter should read between 0.2 and 1.5V as shown in Figure 2 with the accelerator closed, and 4-5V when the accelerator is open.

4. Proceed until you have checked all of the terminals in Chart I, or until a voltage is found that is out of specification. If all voltages are within specification, go to Step 6. If a voltage is out of specification, go to Step 5.

Figure 3:

5. When you find a voltage that is out of specification (except TPS), measure sensor voltage output at the sensor terminal on the same color wire as in the computer terminal for that sensor. Figure 3 shows a typical example. This tells you whether the voltage variation is in the sensor or the connectors and wiring.

Correct any loose connections, replace sensors as required, and then disconnect the battery for 30 seconds to erase the computer's memory of the malfunction. Re-check the appropriate terminal to verify that the malfunction has been corrected.

NOTE: If the TPS voltage is out of specification, remember that the TPS produces a failure signal if the throttle has been blipped when shutting down the engine. Re-start the engine and then let it stop without depressing the accelerator. Then measure the TPS voltage at the computer, and, if necessary, at the sensor connector.

6. Perform the checks in Chart II. If an out-ofspecification voltage is found, measure the sensor output right at the connector. If OK, then you know the wiring or connector is the source of the discrepancy.

NOTE: If the oxygen sensor voltage is out of specification, drive the car until it is warm enough to activate the oxygen sensor and then without shutting off the engine, measure the voltage output of the oxygen sensor at the computer.

7. Correct connections and replace sensors as required, and then disconnect the car's battery for 30 seconds to erase the computer's memory of the malfunction. Re-check the appropriate terminal to verify that the malfunction has been corrected.

NOTE: To avoid damage to the ECU, be sure the ignition is OFF before disconnecting the battery.

1984 FBC SYSTEM VOLTMETER CHECK CHART I

Connector
Terminal Check Item

A-1. Oxygen sensor
A-2. Ground for sensor
A-3. Throttle position sensor +
A-4. Intake air temperature sensor
A-5. Idle position switch (vacuum switch)
A-6. Ground
A-7. Ignition switch
A-8. Ignition switch
A-9. Battery (+)
A-10. Ignition coil (-)
A-11. Ground
A-12. Coolant temperature sensor
A-13. Throttle position sensor (output)
B-1. Jet mixture solenoid valve
B-2. Deceleration solenoid valve
B-3. Idle up control solenoid valve
B-4. Secondary air control solenoid
B-5. Enrichment solenoid valve
B-6. Air conditioner cut relay
B-7. Distributor advance vacuum exchange solenoid valve

1984 FBC SYSTEM VOLTMETER CHECK CHART II