FBC & ECI - Voltmeter Test Procedure: Overview
86mitsubishi02SUBJECT:
1985 AND 1986 FBC AND ECI VOLTMETER TEST PROCEDURE
NO. STB-86-14-007
DATE November 1986
MODEL 1985 and l986 Cordia/Tredia
INTRODUCTION
There are times when it is desirable to test the FBC or ECI system with a voltmeter rather than an ECI Checker - for example, when you want to test the system without first disconnecting the connector to the computer (which erases the computer memory), or when an ECI Checker is unavailable. This bulletin contains a procedure and voltage values for checking the 1985 or 1986 Cordia/Tredia FBC or ECI system with your digital multimeter or any high-impedance voltmeter
FIGURE 1:
VOLTMETER TEST PROCEDURE
Voltages are measured right at the computer. Attach thin wire probes (paper clips are OK) to your voltmeter and insert the probes into the tops of the connectors on the computer as shown in Fig. 1. You don't have to unplug the connectors, but you may find if convenient to pull out the computer to make it easier to reach the connector terminals.
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 prevent this! Insulate the exposed probe with insulating material as a precaution. Step-by-step instructions begin on Page 2.
VOLTMETER TEST PROCEDURE
The test procedure is the same for both the FBC system and the ECI system.
1. Remove any trim panels, etc. to reach the computer terminal connectors.
2. Attach the black lead of your voltmeter to a good ground. One of the computer mounting screw holes would be satisfactory. (Use a jumper to ground the computer box if you have removed it from its mounting for this test).
3. Refer to the ECI and FBC System Check Charts on Pages 6 through 9 of this Bulletin. The illustration below shows what each item in the chart means.
Insert the positive probe of your voltmeter into each connector terminal in turn. Switch the ignition from "LOCK" to "ON" and compare the voltage reading with that shown in the chart; For example, when the probe is on terminal B1 the voltmeter should read System Voltage, i.e., the voltage that is normal for the system under this condition. If you are in doubt as to what is normal, connect the voltmeter from battery + to a good ground. The reading thus obtained is the system voltage.
4. Proceed from one terminal to the next until you have checked all the terminals in Chart 1, or until you have found a voltage out of specification. If you obtain an out-of-specification voltage reading, go to the next step. If not, skip the next step and go on to step 6.
5. When you find a voltage out of specification (except TPS), measure the sensor output at the sensor terminal. This tells you whether the voltage variation is in the sensor or in the connectors and wiring. Be sure the wire color at the sensor is the same as at the computer terminal for that sensor.
Correct any loose connections, replace sensors if required, and then disconnect the battery for 30 sec. to erase the computer's memory of the malfunction. Re-check the appropriate terminal to verify that the malfunction has been corrected.
NOTE: The above step does not apply to the TPS. If TPS voltage is out of specification, adjust it as described in STB-85-14-002. And remember that the TPS produces a failure signal if the throttle is blipped when shutting down the engine. Restart the engine and then let it stop without depressing the accelerator. Measure the TPS voltage at the computer and, if necessary, at the sensor connector.
6. Perform the checks in Chart II, If an out-of-specification voltage is found, locate the sensor and measure its 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. 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: To prevent damage to the computer be sure the ignition switch is OFF before disconnecting the battery cable.
It is not necessary to perform the tests in any prescribed sequence. We recommend beginning with the "ignition lock ON" series and ending with the "idle" series, keeping in mind that some of the tests require the engine to be fully warmed up. For convenience, begin with connector "A" and then go to connector "B".