Engine Controls - System/component Tests: Diagnosis Honda Civic V

Voltage Test

1. Connect test harness between ECU and main wire harness connectors. see scheme 4 Disconnect "B" connector from main harness, but not from ECU. Turn ignition on. Measure voltage between terminals B8 (+) and A18 (-). see scheme 3
2. If voltage is approximately 5 volts, go to next step. If voltage is not as specified, substitute known good ECU, and retest. If voltage reading is now as specified, replace ECU. If voltage reading still is not as specified, check and repair wiring between A/C switch and ECU. See «WIRING DIAGRAMS»(/honda/civic/v-1991-1997/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article in the ENGINE PERFORMANCE Section.
3. Turn ignition off. Reconnect "B" connector to main harness. Turn ignition on. Momentarily connect ECU terminals B3 (+) and A18 (-) together. see scheme 3 If clicking noise is not heard from A/C clutch, go to next step. If clicking noise is heard, start engine and turn A/C on. If A/C operates, A/C signal is present. If A/C does not operate, go to step 5).
4. Using a jumper wire, connect Red/Blue wire from A/C compressor control unit to chassis ground. See «WIRING DIAGRAMS»(/honda/civic/v-1991-1997/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article in the ENGINE PERFORMANCE Section. If clicking noise is heard from A/C clutch, repair open circuit between ECU and A/C compressor control unit. If clicking noise is not heard from A/C clutch, repair A/C system. See «A/C - HEATER SYSTEM - MANUAL»(ref-26368) article in the AIR CONDITIONING & HEAT Section.
5. With engine running and A/C turned on, measure voltage between terminals B8 (+) and A18 (-). If voltage reading is less than one volt, substitute a known good ECU. If A/C now functions, replace ECU. If voltage reading is greater than one volt, repair open circuit between ECU and A/C switch. See «WIRING DIAGRAMS»(/honda/civic/v-1991-1997/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article in the ENGINE PERFORMANCE Section.

Resistance Test

Start engine, and warm to normal operating temperature. Disconnect sensor connector. Using an ohmmeter, measure resistance across sensor terminals. If resistance is not 200-400 ohms, replace sensor.

Functional Test

See EMISSION SYSTEMS & SUB-SYSTEMS .

Disconnect sensor connector. Using an ohmmeter, measure resistance across sensor terminals. Resistance should be as specified. See INTAKE AIR TEMPERATURE (TA) SENSOR RESISTANCE TEST table. If resistance is not within specification, replace sensor.

INTAKE AIR TEMP (TA) SENSOR RESISTANCE TEST

1. Connect test harness between ECU and main wire harness connectors. see scheme 4 Turn ignition switch to ON position. Measure voltage between terminals C11 (+) and C14 (-). see scheme 3
2. If voltage is approximately 3 volts, go to next step. If voltage is not approximately 3 volts, check wiring to sensor for continuity. If wiring is okay, replace MAP sensor.
3. Connect a vacuum pump to MAP sensor, and apply vacuum. If MAP sensor does not hold vacuum, replace sensor.

1. Hold dashpot diaphragm in retracted position using a hand-held vacuum pump. Connect test harness between ECU and ECU wire harness connector. see scheme 4
2. Turn ignition switch to ON position. Measure voltage between ECU terminals C7 (+) and C12 (-). see scheme 3 Open and close throttle while observing voltmeter. Voltage reading should be approximately 0.5 volt with throttle in full closed position and 4.5 volts at wide open throttle. Transition from 0.5 to 4.5 volts should be smooth as throttle is opened.
3. If vehicle is equipped with a manual transmission or is not equipped with an A/T control unit, go to next step. On A/T vehicles equipped with A/T control unit, disconnect 18-pin connector from A/T control unit. Check voltage again as throttle is opened and closed. If voltage does not fluctuate as specified in step 2), go to next step. If voltage now fluctuates as specified, replace A/T control unit.
4. If voltage is not as specified, check for short or open in wire between ECU positive terminal C7 and throttle angle sensor. see scheme 3 If wire is okay, replace throttle angle sensor. If problem still exists, see «G - TESTS W/ CODES»(ref-15658) article in the ENGINE PERFORMANCE Section.

1. Connect test harness between ECU and main harness connector. see scheme 4 Raise vehicle front, and support with safety stands. Connect voltmeter between ECU test harness connector terminals B16 (+) and A18 (-). see scheme 3.
2. Turn ignition switch to ON position. Slowly rotate left front wheel. Voltage should pulsate between zero and 5 volts. If voltage pulsates as specified, go to next step. If voltage does not pulsate, check for open or short in wire between ECU positive terminal B16 and speed sensor. see scheme 3 If wire is okay, replace faulty speed sensor or ECU.
3. Substitute a known good ECU, and recheck. If condition is rectified, replace original ECU.

Scheme 7

1. Remove main relay, located near under-dash fuse box. Using jumper wires, connect battery voltage to terminal No. 4 and ground terminal No. 8 of main relay. (Scheme 7)
2. Using an ohmmeter, check continuity between main relay terminals No. 5 and No. 7. If continuity exists, go to step 3). If continuity does not exist, replace main relay.
3. Connect battery voltage to main relay terminal No. 5 and ground terminal No. 2. Check continuity between terminals No. 1 and No. 3 of main relay. If continuity exists, go to next step. If continuity does not exist, replace main relay.
4. Connect battery voltage to main relay terminal No. 3 and ground terminal No. 8. Check continuity between terminals No. 5 and No. 7 of fuel pump main relay. If no continuity exists, replace main relay. If continuity exists, main relay is okay. If fuel pump still fails to operate, test main relay harness. See «FUEL PUMP MAIN RELAY HARNESS»(ref-15662-S34212554402001010800000) under FUEL SYSTEM.

See also:
• WIRING DIAGRAMS