Engine Controls - Tests W/codes - 2.0l Pgm-Carbureted Honda Prelude III рестайлинг

INTRODUCTION

If no faults were found while performing the test procedures in the BASIC TESTING - CARBURETED article, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE

CHECK ENGINE LIGHT

All models are equipped with a CHECK ENGINE light. As a bulb check, light will illuminate when the ignition is on and engine is not running. CHECK ENGINE light will also illuminate when a system failure has been detected, and a corresponding trouble code has been set in ECU memory. See RETRIEVING CODES .

Not all trouble codes will activate CHECK ENGINE light. If CHECK ENGINE light is on and no codes are flashed by LED on ECU, this indicates that back-up system is in operation. See TESTS W/O CODES article.

With ignition off, insert jumper wire between terminals of 2-pin service check connector, located behind right side of dash. (Scheme 63) Turn ignition on and count flashes on CHECK ENGINE light.

See TROUBLE CODE IDENTIFICATION CHART and proceed to appropriate code for testing. All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated differently in testing procedures.

ECU Indicator LED

If CHECK ENGINE light illuminates when engine is running, a system failure has been detected, and a corresponding trouble code has been set in ECU memory. Access ECU, located under carpet near passenger's side kick panel. Stored codes will be flashed by LED on ECU. To verify codes, see CHECK ENGINE LIGHT .

Not all trouble codes will activate CHECK ENGINE light. If CHECK ENGINE light is on and no codes are flashed by LED on ECU, this indicates that back-up system is in operation. See TESTS W/O CODES article.

ECU LOCATION

The ECU is located under carpet in passenger's side footwell.

TROUBLE CODE IDENTIFICATION MENU

PRELUDE PGM-CARB TROUBLE CODE IDENTIFICATION CHART

Hard Failures

Hard failures cause CHECK ENGINE light to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but loss of good driveability will most likely be encountered.

Intermittent Failures

Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in ECU memory. If related fault does not reoccur within 50 starter operations, related trouble code will be erased from control unit memory. Intermittent failures may be caused by sensor, connector or wiring related problems.

CLEARING CODES

To reset ECU, remove EFI/ECU fuse in under-hood relay box (Prelude PGM-CARB), CLOCK fuse (Prelude PGM-EFI). Leave fuse out for 10 seconds to reset ECU.

Scheme 63

NO CHECK ENGINE LIGHT

1. Turn ignition on. If oil pressure light is on, go to step 2). If light is off, inspect fuse No. 13. If fuse is okay, repair open circuit in Yellow wire between fuse and combination meter.
2. Turn ignition off. Connect ECU Test Harness (07LAJ-PT30100 ) connector between ECU and harness connectors. (Scheme 63) Connect Test Harness terminal D3 to ground. Turn ignition on. If CHECK ENGINE light comes on, go to step 3). If light still fails to come on, replace light bulb or repair open in Yellow/Red wire between ECU terminal D3 and combination meter.
3. Jumper terminals D3 and A26. CHECK ENGINE light should stay on. If it does, go to step 4). If light does not stay on, repair Black wire between ECU terminal A26 and ground.
4. If CHECK ENGINE light is still on, substitute a known good ECU. If condition is corrected, replace original ECU.

CHECK ENGINE LIGHT ON, LED DOES NOT FLASH CODES

1. Turn ignition on. Check charging system warning light. If charging light is off, inspect No. 12 fuse. If fuse is okay, repair open Black/Yellow wire between No. 12 fuse and combination meter. If charging system warning light is on, go to step 2).
2. Turn ignition off. Connect ECU Test Harness between ECU and ECU connectors. (Scheme 63) Attach connector "A" to ECU wiring harness side only. Turn ignition on. Check if CHECK ENGINE light comes on. If it does, repair short on Yellow/Red wire between ECU terminal D3 and combination meter. If light is not on, go to next step.
3. Connect ECU Test Harness connector "D" to ECU. Disconnect 3-wire MAP connector. Check ECU LED inspection light. If LED inspection light flashes Code 3, replace MAP sensor. If Code 3 is not present, go to next step.
4. On automatic transmission models, reconnect 3-wire MAP sensor connector. Disconnect 3-wire throttle angle sensor connector. If CHECK ENGINE light still stays on, go to step 5). If light is not on, replace throttle angle sensor.
5. Disconnect connector "A" from A/T control unit. If CHECK ENGINE light turns off, replace A/T control unit. If light does not turn off, disconnect 3-wire MAP sensor connector and go to next step.
6. On all models, turn ignition off. Disconnect connector "D" from ECU side. Check continuity between body ground and Test Harness terminal D20. If continuity is present, go to next step. If continuity is not present, go to step 8).
7. On manual transmission models, repair short to ground in Yellow/White wire between ECU terminal D20 and MAP sensor. On A/T models, repair short to ground in Yellow/White wire between ECU terminal D20 and throttle angle sensor or A/T control unit or MAP sensor.
8. If continuity was not present, reconnect connector "D" to ECU and 3-wire connector to MAP sensor. On automatic transmission models, reconnect 3-wire connector to throttle angle sensor and connector "A" to A/T control unit.
9. On all models, turn ignition on. Measure voltage between ECU connector terminal A23, A25 and ground. If battery voltage is present, substitute a known good ECU and recheck. If condition is corrected, replace ECU. If battery voltage is not present, repair open in Black/Yellow wire between ECU terminals A23, A25 and No. 12 fuse.

Scheme 64

1. Warm engine to normal operating temperature (until cooling fan comes on). Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU.
2. Start engine and allow to idle for one minute. Raise engine speed to 3000 RPM. Quickly remove vacuum hoses No. 2 and No. 7 from vacuum hose manifold. Plug vacuum ports. (Scheme 64) Hold engine speed at 3000 RPM for 20 seconds. Verify if CHECK ENGINE light is on and if LED is flashing Code 1. If light is and LED is flashing Code 1, go to next step. If LED is not flashing Code 1, problem is intermittent. Check connectors at O2 sensor, battery, and at ECU.
3. Turn ignition off. Disconnect O2 sensor wire harness and connect voltmeter between O2 sensor connector and ground. Start engine. Measure voltage between O2 sensor connector and ground.
4. Voltage should be greater than.6 volt at wide open throttle, and less than.4 volt when throttle is quickly released. If not within specification, replace O2 sensor. If okay, proceed to next step.
5. Turn ignition off and reconnect O2 sensor. Attach ECU Test Harness connector between ECU and ECU connector. (Scheme 63) Start and warm engine. Using a voltmeter, measure voltage between ECU test harness terminals D13 (positive) and D21 (negative).
6. Momentarily open throttle wide open, then close throttle quickly. Voltage at wide open throttle should be greater than.6 volt, and less than.4 volt at closed throttle. If okay, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
7. If voltage was not as specified in step 6), repair open or short circuit in White wire between ECU terminal D13 and O2 sensor.

CODE 2 - VEHICLE SPEED SENSOR (VSS)

1. Connect ECU Test Harness connector between ECU and wiring harness connectors. (Scheme 63) Block rear wheels and set parking brake. Raise front end of vehicle and support with stands. Turn ignition on.
2. Slowly rotate left front wheel and measure voltage between ECU terminals D9 (positive) and D21 (negative). If voltage pulses from zero to 5 volts, proceed to step 5). If voltage does not pulse, turn ignition off and go to next step.
3. Disconnect ECU Test Harness connector from ECU side. Turn ignition on. Slowly rotate left front wheel and measure voltage between ECU terminals D9 (positive) and A25 (negative). Voltage should pulse from zero to 12 volts. If voltage pulses, substitute a known good ECU and recheck. If condition is corrected, replace original ECU. If voltage did not pulse, go to next step.
4. If from step 3), voltage did not pulse from zero to 12 volts, repair open or short in White/Blue wire between ECU terminal D9 and VSS. If wires are okay, replace VSS.
5. If from step 2), voltage pulses from zero to 5 volts, increase engine speed to 3000 RPM with no load. If code is reset, check No. 7 vacuum hose on vacuum manifold, and vacuum switch for leaks. (Scheme 64) If hose and switch are okay, substitute a known good ECU. If condition is corrected, replace original ECU.

CODE 3 - MAP SENSOR

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Start and warm engine to normal operating temperature. Verify if CHECK ENGINE light is on and if LED is flashing Code 3. If LED is not flashing Code 3, problem is intermittent. Test drive and check CHECK ENGINE light again.
2. If LED is flashing Code 3, turn ignition off. Connect 3-wire Test Harness (07GMJ-ML80100 ) connector between MAP sensor and sensor harness. Turn ignition on. Measure voltage between Red (positive) and Green (negative) terminals. If reading is about 5 volts, go to step 3). If reading is not about 5 volts, measure voltage between Red (positive) terminal and ground.
3. If measured voltage is approximately 5 volts, repair open in Green/White wire between ECU terminal D22 and MAP sensor. If voltage is not 5 volts, turn ignition off. Connect ECU Test Harness connector between ECU connectors. (Scheme 63) Turn ignition on.
4. Measure voltage between ECU terminal D20 (positive) and D22 (negative). If measured voltage is approximately 5 volts, repair open in Yellow/White wire between ECU terminal D20 and MAP sensor. If voltage is not 5 volts, substitute a known good ECU. If condition is corrected, replace original ECU.
5. Measure voltage between White (positive) and Green (negative) terminals. If reading is not about 3 volts, replace MAP sensor or repair open or short in White/Blue wire between ECU terminal D17 and MAP sensor.
6. If measured voltage is about 3 volts, turn ignition off. Connect ECU Test Harness connector between ECU connectors. (Scheme 63) Turn ignition on. Measure voltage between terminals D17 (positive) and D22 (negative). If 3 volts are not present, repair open in White/Blue wire between ECU terminal D17 and MAP sensor. If not go to step 7).
7. If 3 volts was present, substitute a good known ECU and retest. If condition is corrected, replace original ECU.

Scheme 65

1. Turn ignition off. Remove EFI/ECU fuse in under-hood fuse relay box for 10 seconds to reset ECU. Start engine and allow to idle for at least 30 seconds. Verify if CHECK ENGINE light is on and if LED is flashing Code 4. If LED is not flashing Code 4, problem is intermittent. Test drive and check light again.
2. If LED is flashing Code 4, turn ignition off. Disconnect 8-wire connector at control box. Check resistance between terminals No. 5 and 6 of control box. (Scheme 65) Continuity should exist. If continuity exists, go to step 4).
3. If continuity does not exist, remove vacuum hose No. 7 from vacuum manifold and connect a "T" fitting and vacuum pump/gauge. (Scheme 66) Start engine and read vacuum gauge at idle. If reading is more than 1.2 Hg, check routing of No. 7 vacuum hose. If reading does not exceed 1.2 in. Hg, replace vacuum switch and repair open in Black/Yellow or White wire in control box.
4. Turn ignition on. Measure voltage between Black/Yellow terminal and ground. Battery voltage should be present. If battery voltage is not present, repair open in Black/Yellow wire between vacuum switch 8-wire connector and fuse No. 12.
5. If battery voltage was present, turn ignition off. Reconnect vacuum switch 8-wire connector to control box. Connect ECU Test Harness connector between ECU connectors. (Scheme 63) Turn ignition on. Measure voltage between terminal D7 (positive) and D21 (negative).
6. Battery voltage should be present. If battery voltage is not present, repair open in Light Blue wire between control unit D7 and vacuum switch. If battery voltage was present, substitute with a known good ECU and recheck. If condition is corrected, replace original ECU.

Scheme 66

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Start engine and hold at idle. Verify if CHECK ENGINE light is on and if LED is flashing Code 5. If LED is not flashing Code 5, problem is intermittent. Test drive vehicle and check light again.
2. If CHECK ENGINE light is on and Code 5 is still present, turn ignition off. Install "T" fitting in No. 2 vacuum hose between vacuum manifold and MAP sensor. Connect vacuum gauge to "T" fitting. (Scheme 66) Start engine. If vacuum is not present, repair as necessary. If engine vacuum is present, connect vacuum pump to "T" fitting. Apply vacuum and check if vacuum holds.
3. If vacuum is held, go to step 4). If vacuum does not hold, connect vacuum pump directly to MAP sensor. Apply vacuum. If MAP sensor holds vacuum, replace vacuum hose to port. If MAP sensor does not hold vacuum, replace MAP sensor.
4. Connect 3-wire test connector between MAP sensor and wiring harness. Turn ignition on. Measure voltage between White (positive) and Green (negative) sensor terminals. If reading is not about 3 volts, replace MAP sensor. If reading is about 3 volts, substitute a known good ECU. If condition is corrected, replace original ECU.

CODE 6 - COOLANT TEMPERATURE (TW) SENSOR

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 6. If LED is not flashing Code 6, problem is intermittent. Test drive vehicle and observe CHECK ENGINE light again.
2. If LED is flashing Code 6, warm engine to normal operating temperature (until cooling fan comes on). Disconnect 2-wire coolant sensor connector. Measure resistance across sensor terminals.
3. If resistance is not 200-400 ohms, replace coolant sensor. If resistance is 200-400 ohms, measure voltage between ground and Yellow/Green wire of sensor harness. If voltage reading is about 5 volts, go to step 4). If 5 volts are not present, go to step 5).
4. Measure voltage between Yellow/Green (positive) and Green/White (negative) terminals. If voltmeter now reads 5 volts, substitute a known good ECU and recheck. If condition is corrected replace original ECU. If 5 volts are not present, repair open in Green/White wire between ECU terminal D22 and coolant sensor.
5. Turn ignition off. Connect ECU Test Harness connector between ECU and ECU connectors. Turn ignition on. Measure voltage between terminals D15 (positive) and D22 (negative). (Scheme 63) If voltage reading is about 5 volts, repair open Yellow/Green wire between ECU terminal D15 and TW sensor.
6. If reading is not about 5 volts, disconnect ECU Test Harness connector from main wire harness side. Measure voltage between terminals D15 (positive) and D22 (negative). If reading is not about 5 volts, go to step 7). If voltage reading is about 5 volts, repair short in Yellow/Green wire between ECU terminal D15 and TW sensor or between TW sensor and A/T control unit.
7. If about 5 volts still is not read, substitute a known good ECU. If condition is corrected, replace original ECU.

CODE 7 - CLUTCH SWITCH SIGNAL (M/T)

1. Warm engine to normal operating temperature (until cooling fan comes on). Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Road test with transmission in 4th gear. Accelerate to 3000 RPM and then decelerate to 2000 RPM over 5-7 seconds.
2. Verify if CHECK ENGINE light is on and if LED is flashing Code 7. If LED is not flashing Code 7, problem is intermittent. Test drive vehicle and observe CHECK ENGINE light again. If CHECK ENGINE light is on and LED is flashing Code 7, turn ignition off. Connect ECU Test Harness between control unit and connector. (Scheme 63) Turn ignition on. Measure voltage between terminals D8 (positive) and D21 (negative).
3. If voltage is greater than one volt, go to step 4). If voltage is less than one volt, depress clutch pedal and recheck voltage. If battery voltage is not present, go to step 5). If battery voltage is present, substitute a known good control unit and retest. If condition is corrected, replace original ECU.
4. Turn ignition off. Disconnect 2-wire connector on clutch switch. Connect Black/Red terminal to Black terminal. Turn ignition switch to ON position. If voltage is now less than one volt, replace clutch switch. If voltage is not less than one volt, repair open in Black/Red, Orange wire between ECU terminal D8 and clutch switch or Black wire between clutch switch and ground.
5. Turn ignition switch off. Disconnect "D" connector from main wire harness only, not from control unit. Turn ignition on. Recheck voltage between terminals D8 and D21. If battery voltage is present, go to next step. If battery voltage is not present, substitute a known good control unit and recheck. If battery voltage is now available, replace original control unit.
6. Reconnect "D" connector to main wire harness and disconnect 2-wire connector on clutch switch. If battery voltage is now present, replace clutch switch. If battery voltage is still not present, repair short in Black/Red, Orange wire between ECU terminal D8 and clutch switch.

CODE 7 - A/T SHIFT POSITION SIGNAL (A/T)

1. Turn ignition on and observe A/T shift indicator, while selecting each gear position. If A/T shift position indicator does not light properly, inspection of shift position indicator is necessary. If indicator lights properly, start engine and warm to normal operating temperature (cooling fan comes on). Turn ignition off.
2. Remove EFI, ECU fuse in underhood relay box for 10 seconds to reset control unit. Road test with shift selector in S3, accelerate to 3500 RPM then decelerate to 2000 RPM over 5 to 7 seconds. If CHECK ENGINE light is not on and LED does not indicate Code 7, the failure is intermittent and a test drive may be necessary for further diagnosis.
3. If CHECK ENGINE light is on and the LED indicates Code 7, turn ignition off. Connect ECU Test Harness between control unit and connector. (Scheme 63) Measure voltage between terminals D10 (positive) and D21 (negative) with gear selector in Neutral or Park position.
4. If voltage is present, repair open in Light Green wire between control unit terminal D10 and combination meter. If voltage is not present, measure voltage between terminals D10 and B8 with gear selector in all positions except Neutral or Park. If battery voltage is present, substitute a known good control unit and retest. If condition is corrected, replace original ECU. If battery voltage is not present, check for a short in Light Green wire between combination meter and control unit terminal D10.

Scheme 67

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay box for 10 seconds to reset ECU. Start engine and allow to idle. Verify if CHECK ENGINE light is on and LED is flashing Code 8. If LED is not flashing Code 8, problem is intermittent. Check connections at ignition coil and ECU.
2. If CHECK ENGINE light is on and Code 8 is present, turn ignition off. Disconnect ignition coil primary terminals. Measure resistance between ignition coil terminals "B" and "D". (Scheme 67) If resistance is not about 2000 ohms, replace coil. If okay, reconnect primary connectors.
3. Connect ECU Test Harness connector to main wire harness side. Turn ignition on. Measure voltage between terminals A9 (positive) and D21 (negative). If reading is about 10 volts, substitute a known good ECU and recheck. If condition is corrected, replace ECU. If condition is not corrected, repair open Blue wire between ECU terminal A9 and ignition coil.

CODE 10 - INTAKE AIR TEMPERATURE (TA) SENSOR

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Start engine and observe CHECK ENGINE light. If light is off, problem is intermittent. Test drive vehicle and check again.
2. If CHECK ENGINE light is on and LED is flashing Code 10, turn ignition off. Measure resistance across TA sensor terminals. If reading is not 1000-4000 ohms, replace TA sensor. If reading is 1000-4000 ohms, measure voltage between White/Red (positive) terminal and ground. If reading is about 5 volts, go to step 3). If reading is not about 5 volts, go to step 4).
3. Measure voltage between White/Red (positive) and Green/White (negative) wire terminals. If voltage is not about 5 volts, repair open in Green/White wire between ECU terminal D22 and sensor. If reading is about 5 volts, substitute a known good ECU. If condition is corrected, replace original ECU.
4. Turn ignition off. Connect ECU Test Harness connector between ECU and ECU connectors. (Scheme 63) Turn ignition on. Measure voltage between ECU terminals D18 (positive) and D22 (negative). If 5 volts are present, repair open in White/Red wire between ECU terminal D18 and TA sensor. If 5 volts are not present, go to step 5).
5. If reading was not about 5 volts, disconnect ECU test connector "D" from main wire harness side. Measure voltage between terminals D18 (positive) and D22 (negative). If voltage reading is about 5 volts, repair short in White/Red wire between ECU terminal D18 and TA sensor.
6. If voltage is not about 5 volts, substitute a known good ECU. If voltage is now correct, replace original ECU.

CODE 14 - ELECTRONIC AIR CONTROL VALVE (EACV)

1. Turn ignition off. Remove EFI/ECU fuse in under-hood relay panel for 10 seconds to reset ECU. Start engine and raise engine speed to 3500 RPM, then close throttle suddenly. observe CHECK ENGINE light. If light is off, problem is intermittent. Test drive vehicle and check again.
2. If CHECK ENGINE light is on and LED is flashing Code 14, turn ignition off. Disconnect EACV connector. Check resistance between the 2 connector terminals on valve.
3. Resistance should be between 8-15 ohms. If resistance is not 8-15 ohms, replace EACV. If resistance reading is 8-15 ohms, check continuity on each EACV terminal to ground. If continuity is present, replace EACV. If continuity is not present, go to step 4).
4. Reconnect EACV 2-wire connector. Connect ECU Test Harness to ECU connector, but not ECU. (Scheme 63) Check for continuity between terminals A24, A26 and ground. If continuity does not exist, repair open Black wire between ECU terminals A24, A26 and ground.
5. If continuity exists, measure resistance between terminals A3 and A1. Resistance should be 8-15 ohms. If resistance is not 8-15 ohms, repair open in Blue/Red wire between ECU terminal A1 and EACV or Yellow/Black wire between ECU terminal A3 and EACV. If resistance is okay, substitute a known good ECU. If condition is corrected, replace original ECU.

Scheme 68

SUMMARY

If no hard fault codes are present, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO-START, etc.) or intermittent diagnosis procedures.

See also:
• BASIC TESTING - CARBURETED
• TESTS W/O CODES
• RETRIEVING CODES
• 2
• 3
• 6
• 7
• 7
• 10
• 14