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

Testing & Diagnostics 3 illustrations ~5819 words

INTRODUCTION

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

CHECK ENGINE LIGHT

All models are equipped with a CHECK ENGINE light. (Scheme 69) 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 69) Turn ignition on and count flashes on CHECK ENGINE light.

See PRELUDE FUEL INJECTION 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

Code (1)System AffectedProbable Cause
0 (2)ECUNo signal to ECU
1Oxygen Sensor AProblem in O2 sensor circuit
2Oxygen Sensor BProblem in O2 sensor circuit
3MAP SensorElectrical problem in MAP sensor
4Crank Angle SensorProblem in CRANK circuit of sensor
5MAP SensorMechanical problem in MAP sensor
6Coolant Temperature SensorOpen or shorted circuit signal
7Throttle Angle SensorOpen or shorted signal circuit
8TDC SensorProblem in TDC circuit of sensor
9No. 1 Cyl. Position SensorProblem in CYL ckt of sensor
10Intake Air TemperatureOpen or shorted circuit signal
12EGR SystemNo EGR action
13Atmospheric PressureOpen or shorted circuit signal
14Electronic Air Control (EACV)Open or shorted EACV ckt
15Ignition Output SignalOpen or shorted signal circuit
16Fuel InjectorOpen or shorted signal circuit
17Vehicle Speed SensorOpen or shorted signal circuit
(1) If codes other than the above are indicated, repeat self-diagnosis. If code(s) reappear, substitute with a known good ECU and recheck code(s). If code(s) clear, replace ECU. (2) NO CHECK ENGINE LIGHT, CHECK ENGINE LIGHT ON, LED DOES NOT FLASH CODES
(1)If codes other than the above are indicated, repeat self-diagnosis. If code(s) reappear, substitute with a known good ECU and recheck code(s). If code(s) clear, replace ECU.
(2)NO CHECK ENGINE LIGHT, CHECK ENGINE LIGHT ON, LED DOES NOT FLASH CODES

PRELUDE FUEL INJECTION 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 CLOCK fuse (Prelude PGM-EFI). Leave fuse out for 10 seconds to reset ECU.

Scheme 69

Scheme 69: HARNESS CONNECTOR ID
Scheme 69: HARNESS CONNECTOR ID

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 between ECU and connector. (Scheme 69) Connect terminal B6 to ground. Turn ignition on. If CHECK ENGINE light is now on, go to step 3). If light is off, replace light bulb or repair open in Green/Red wire between ECU terminal A13 and combination meter.
  3. Individually connect ECU terminal A2 and then terminal A4 to terminal B6. If CHECK ENGINE light fails to illuminate, repair open in Black A2 or A4 wires between ECU and ground.
  4. If CHECK ENGINE light illuminated in step 3), substitute a known good ECU. If condition is corrected, replace original ECU.

CHECK ENGINE LIGHT ON

  1. Turn ignition on. One at a time, disconnect the 3-wire connectors at MAP sensor, throttle angle sensor and EGR position sensor. If LED remains lit, go to step 2). If LED goes out, replace sensor which caused LED to go out when unplugged.
  2. Reconnect all connectors. Disconnect 3-wire connector at Atmospheric Pressure (PA) sensor. If LED flashes Code 13 when sensor is disconnected, replace faulty sensor. If code for disconnected sensor was not flashed, go to the next step.
  3. Turn ignition off. Reconnect connector(s). Connect ECU Test Harness connectors between ECU and ECU harness. (Scheme 69) Disconnect connector "C" from ECU side. Check continuity between ground and terminals C13 and C15. If continuity does not exist, go to step 4). If continuity exists, repair short to ground in Red/White wire from terminal C15 to MAP sensor, or in Yellow/White wire from terminal C13 to PA sensor or EGR position sensor.
  4. Reconnect connector "C". Disconnect connector "B" from ECU side. Turn ignition on. If LED comes on, repair short to ground in Yellow/Red (Prelude) wire between ECU terminal B6 and combination meter. If LED is not on, connect terminal B6 to terminal A16 and then to terminal A18, one at a time. If LED illuminates, go to step 5). If LED does not illuminate, repair individual ground connections which did not make light come on (A18 or A16).
  5. Measure voltage between terminal A15 (positive) and A18 (negative). If battery voltage is not present, repair open Yellow/Black (Prelude) A15 wire between ECU and main relay, or repair main relay or relay wiring. If battery voltage is present, substitute a known good ECU. If condition is corrected, replace original ECU.

Prelude 2.0L

  1. Turn off ignition. Reset ECU by removing HAZARD fuse in main fuse box or CLOCK fuse in under-hood relay box for 10 seconds. Start engine. Check fuel pressure at fuel filter. See «BASIC TESTING - FUEL INJECTED»(/honda/prelude/iii-1989-1992/remont/testing-diagnostics/#engine-controls-basic-testing-fuel-injected) article. Repair fuel system if not within specification. If fuel pressure is within specification, proceed to next step.
  2. Bring engine to operating temperature (cooling fan comes on). Hold engine speed at 1500 RPM (minimum) for 15 minutes, without closing throttle completely during this time.
  3. Check if CHECK ENGINE light is on. If light is not on, problem is intermittent. Test drive and check light again. If light is on, disconnect indicated O2 sensor connector. Attach voltmeter to vehicle ground and O2 sensor connector. With engine at normal operating temperature, momentarily open throttle wide open, then close throttle.
  4. Voltage at wide open throttle should be greater than.6 volt, and less than.4 volt at closed throttle. If not within specifications, replace oxygen sensor. If voltage is within specifications, proceed to next step.
  5. Turn ignition off. Reconnect O2 sensor connector. Attach ECU Test Harness between ECU and ECU connector. (Scheme 69) Restart and warm engine to normal operating temperature. Hold engine speed at 4000 RPM for 10 seconds and close throttle completely.
  6. Measure voltage between ECU terminals C16 (positive) and A18 (negative) for O2 sensor "A" and ECU terminals B11 (positive) and A18 (negative) for O2 sensor "B".
  7. Voltage at wide open throttle or 4000 RPM should be greater than.6 volt, and less than.4 volt at closed throttle. If not within specification, repair wire between ECU and oxygen sensor(s). If within specification, substitute a known good ECU. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and warm to normal operating temperature (cooling fan on). Verify if CHECK ENGINE light is on and if LED is flashing Code 3. If LED is flashing Code 3, go to next step. If LED is not flashing Code 3, problem is intermittent. Check connectors at MAP sensor and at ECU.
  2. Turn ignition off. Disconnect 3-wire connector from MAP sensor. Turn ignition on. Measure voltage between Red/White (positive) and ground. If reading is about 5 volts, go to step 3). If reading is not about 5 volts, repair open in Red/White wire between ECU terminal C15 and MAP sensor. If wire is okay, substitute a known good ECU. If condition is corrected, replace original ECU.
  3. Measure voltage between Red/White (positive) and Blue/White (negative) terminals. If about 5 volts are present, go to step 4). If about 5 volts is not present, repair open in Blue/White wire between ECU terminal C14 and MAP sensor. If wire is okay, substitute a known good ECU. If condition is corrected, replace original ECU.
  4. Measure voltage between White/Blue (positive) and Blue/White (negative) terminals. If voltage is about 5 volts, go to step 5). If about 5 volts are not present, repair open in White/Blue wire between ECU terminal C11 and MAP sensor. If wire is okay, substitute a known good ECU. If condition is corrected, replace original ECU.
  5. Turn ignition off. Reconnect 3-wire connector to MAP sensor. Connect ECU Test Harness between ECU and ECU harness. (Scheme 69) Turn ignition on. Measure voltage between terminal positive C11 and negative C14. If reading is not about 3 volts, replace MAP sensor.
  6. If there is about 3 volts present, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.

Scheme 70

Scheme 70: Prelude 2.0L
Scheme 70: Prelude 2.0L
  1. Turn ignition off. Remove or CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 4. If LED is flashing Code 4, go to next step. If LED is not flashing Code 4, problem is intermittent. Check connectors at distributor and related circuits.
  2. Turn ignition off. Disconnect 4-wire TDC/CRANK sensor connector nearest the sensor. Measure resistance across terminals "C" and "D" at sensor. (Scheme 70) If reading is not 700-1000 ohms, replace pulse generator assembly. If reading is within specification, proceed to next step.
  3. Check continuity between ground and sensor terminals "C" and "D" individually. If continuity exists on either terminal, sensor is shorted to ground. Replace pulse generator assembly. If no continuity exists, go to next step.
  4. Reconnect sensor connector. Connect ECU Test Harness to main harness side only. (Scheme 69) Check resistance between connector terminals B10 and B12. Resistance should be 700-1000 ohms.
  5. If resistance is not within specification, repair open in Blue/Yellow and/or Blue/Green wire. If resistance is within specification, check for continuity from terminal B10 to ground.
  6. If continuity exists, repair short in Blue/Green wire between ECU terminal B10 and distributor. If continuity does not exist, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 5. If LED is flashing Code 5, go to next step. If LED is not flashing Code 5, problem is intermittent. Check vacuum hoses, pipes and connections. Ensure all connectors are secure.
  2. Turn ignition off. Using a "T" fitting, connect a hand-held vacuum pump/gauge into vacuum hose between throttle body and MAP sensor (vacuum hose No. 21). Apply vacuum. If vacuum does not hold, attach vacuum pump/gauge directly to MAP sensor. Apply vacuum. If vacuum does not hold, replace MAP sensor. If vacuum holds, check MAP sensor vacuum hose for cracks, splits or looseness. Repair as necessary.
  3. Check vacuum supply to MAP sensor with engine running. If vacuum is not present, repair hose or clear restriction from throttle body. If vacuum supply is okay, turn ignition off.
  4. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Measure voltage between positive terminal C11 and negative terminal C14. If voltage reading is about 3 volts, go to next step. If voltage is not about 3 volts, replace MAP sensor.
  5. Start engine and let idle. If voltage is not about 1 volt, replace MAP sensor. If voltage reading is about 1 volt, substitute a known good ECU. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box 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 flashing Code 6, go to next step. If LED is not flashing Code 6, problem is intermittent. Check connectors at TW sensor and related circuits.
  2. Start engine and warm to normal operating temperature (cooling fan comes on). Turn ignition off. Disconnect 2-wire coolant sensor connector. Measure resistance across sensor terminals.
  3. If resistance is not 200-400 ohms, replace TW sensor. If resistance is within specification, turn ignition switch on. Measure voltage between ground and Yellow/Green wire TW sensor harness. If reading is about 5 volts, go to step 4). If reading is not about 5 volts, go to step 5) for A/T models or step 6) for M/T models.
  4. Measure voltage between Yellow/Green (positive) wire and Green/White (negative) terminals. If reading is about 5 volts, substitute a known good ECU and recheck. If condition is corrected, replace original ECU. If voltage reading is not as specified, repair open Green/White wire between ECU terminal C12 and TW sensor.
  5. Disconnect 18-wire connector from A/T control unit. If voltage is now about 5 volts, replace A/T control unit. If reading is not about 5 volts, repair open or short in Yellow/Green wire between ECU terminal C6 A/T control unit and TW sensor. If wire is okay, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  6. Repair open or short in Yellow/Green wire between ECU terminal D13 and TW sensor. If wire is okay, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 7. If LED is flashing Code 7, go to next step. If LED is not flashing Code 7, problem is intermittent. Check connectors at throttle angle sensor and related circuits.
  2. Turn ignition off. Disconnect 3-wire connector at throttle position sensor. Turn ignition on. Measure voltage between Yellow/White (positive) and Green/White (negative) terminals. If voltage is not about 5 volts, go to step 6). If voltage is about 5 volts, turn ignition off. Reconnect sensor connector. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69)
  3. Turn ignition on. Measure voltage between positive terminal C7 and negative terminal C12. Voltage should read.5 volt at closed throttle, and about 4.5 volts at wide open throttle, with a smooth transition between the lower and upper voltage specification as the throttle is depressed.
  4. If throttle sensor responds as indicated, substitute a known good ECU. If condition is corrected, replace original ECU. If sensor does not respond as indicated in step 3), replace throttle sensor or repair open or short in Red/Black (Prelude) wire between ECU terminal C7 and throttle sensor. On Prelude A/T models, go to step 5).
  5. Disconnect 18-wire connector from A/T control unit. If throttle sensor now responds as indicated, replace A/T control unit. If throttle sensor does not respond as indicated, check for open or short in Red/Black wire between ECU terminal D11, throttle angle sensor and A/T control unit.
  6. If voltage reading between Yellow/White (positive) and Green/White (negative) terminals in step 2) was not about 5 volts, measure voltage between ground and Yellow/White wire terminal. If voltage is now about 5 volts, repair open in Green/White wire between ECU terminal C12 and throttle sensor. If reading is not about 5 volts, turn ignition off.
  7. Connect ECU Test Harness between ECU and ECU connector. Turn ignition on. Measure voltage between positive terminal C13 and negative terminal C12. If voltage is about 5 volts, repair open Yellow/White wire between ECU terminal C13 and throttle sensor. If reading is not about 5 volts, substitute a known good ECU. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe CHECK ENGINE light. If light is off, problem is intermittent. Test drive and check again.
  2. If light is on, turn ignition off. Disconnect 4-wire sensor connector at distributor. Measure resistance between Orange/Blue and White/Blue terminals. If reading is not 700-1000 ohms, replace pulse generator assembly. If reading is within specification, proceed to next step.
  3. Check continuity between ground and Orange/Blue wire terminal. Check continuity between ground and White/Blue wire terminal. If continuity exists, sensor is shorted to ground. Replace pulse generator assembly. If no continuity exists, proceed to next step.
  4. Reconnect sensor connector. Attach ECU Test Harness to main wire harness side only. (Scheme 69) Using an ohmmeter, check resistance between connector C3 and C4 terminals. Resistance should be 700-1000 ohms.
  5. If resistance is not within specification, repair open or short in Orange/Blue and/or White/Blue wire. If resistance is within specification, check for continuity from terminal C3 to ground.
  6. If continuity exists, repair short in Orange/Blue wire between ECU terminal C3 and sensor connector. If continuity does not exist, substitute a known good ECU. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 9. If LED is flashing Code 9, go to next step. If LED is not flashing Code 9, problem is intermittent. Check connectors at distributor and related circuits.
  2. Turn ignition off. Disconnect 2-wire sensor connector. Measure resistance across sensor terminals. If reading is not 700-1000 ohms, replace CYL sensor assembly. If reading is within specification, proceed to next step.
  3. Check continuity between ground and each sensor terminal. If continuity exists, replace CYL sensor assembly. If no continuity exists, proceed to next step.
  4. Reconnect sensor connector. Attach ECU Test Harness to main wire harness side only. Check resistance between connector terminals C1 and C2. Resistance should be 700-1000 ohms.
  5. If resistance is not within specification, repair open or short in Orange and/or White wires. If resistance is within specification, check continuity between terminal C1 and ground. If continuity is not present, repair open in Orange wire between ECU terminal C1 and CYL sensor connector. If resistance is within specification, substitute a known good ECU and retest. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 10. If LED is flashing Code 10, go to next step. If LED is not flashing Code 10, problem is intermittent. Check connectors at TA sensor and related circuits.
  2. If light is on, turn ignition off. Disconnect TA sensor connector and measure resistance across TA sensor terminals. If resistance reading is not 1000-4000 ohms, replace TA sensor. If resistance reading is within specification, disconnect ohmmeter and turn ignition on. Measure voltage between ground and Red/Yellow wire terminal. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 4).
  3. Measure voltage between Red/White (positive) and Green/White (negative) terminals. If voltage is not about 5 volts, repair open circuit in Green/White wire between ECU terminal C12 and TA sensor. If voltage is about 5 volts, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  4. Repair open or short in Red/Yellow wire between ECU terminal C5 and TA sensor. If wire is okay, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  1. Turn ignition off. Remove remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and warm to normal operating temperature. Road test vehicle for about 10 minutes. Try to keep engine speed in 1700-2500 RPM range. Verify if CHECK ENGINE light is on and if LED is flashing Code 12. If LED is flashing Code 12, go to next step. If LED is not flashing Code 12, problem is intermittent. Check connectors at EGR valve and related circuits.
  2. With engine at idle, disconnect vacuum hose (No. 16) from EGR valve. Using a hand-held vacuum pump/gauge, test for vacuum. If vacuum is not present, go to step 5). If vacuum is present, go to next step.
  3. Disconnect 4-wire connector from vacuum control box and again check for vacuum. If vacuum is present, check vacuum hose routing for entire EGR system. If hose routing is okay, replace EGR solenoid control valve.
  4. If vacuum was not present, check for short to ground in Red wire between EGR solenoid control valve and ECU terminal B5. If wire is okay, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  5. Move vacuum pump to EGR valve and apply 8 in. Hg to EGR valve. If vacuum does not hold, and engine does not stall, replace faulty EGR valve or clean blocked EGR passages.
  6. If vacuum held and engine stalled in step 5), disconnect 4-wire connector from control box. Measure voltage between Black/Yellow (positive) terminal on main wire harness and ground. Battery voltage should be present. If battery voltage is not present, repair open in Black/Yellow wire between solenoid valve and fuse No. 12 (Prelude). If battery voltage is present, go to next step.
  7. Reconnect vacuum pump/gauge to EGR vacuum hose (No. 16). Start engine and let idle. Supply battery voltage to Black/Yellow wire terminal of box and ground to Red wire terminal of box. Reading at EGR valve hose should be about 8 in. Hg after one second. If reading is okay, go to step 10). If not, go to step 8).
  8. Turn ignition off. Inspect hoses No. 16 and 24 for leaks, restrictions and misrouting. If problem is found, repair as necessary. If hoses are okay, disconnect lower hose on EGR control solenoid valve and connect a vacuum gauge.
  9. Start engine and allow to idle. If 6-10 in. Hg is not present, replace Constant Vacuum Control Valve (CVC). If 6-10 in. Hg is present, replace EGR control solenoid valve.
  10. If gauge read 8 in. Hg in step 7), turn ignition off and reconnect 4-pin connector. Connect Test Harness (07GMJ-ML80100 ) to EGR lift sensor harness. Turn ignition on. Measure voltage between Red (positive) and Green (negative) wire terminals. If about 5 volts is not present, repair open in Yellow/White wire between ECU terminal C13 and EGR valve or Green/White wire between ECU terminal C12 and EGR valve.
  11. If 5 volts is present, measure voltage between White (positive) and Green (negative) wire terminals. If approximately 1.2 volts is not present, replace EGR valve. Repair short in White/Black or Yellow wire between ECU terminal C8 and EGR lift sensor. If wire is okay, substitute a known good ECU. If proper voltage is present, replace original ECU.
  12. If 1.2 volts is present, observe voltmeter and slowly apply a continuous 8 in. Hg to valve. Repeat several times, fully releasing vacuum between checks. If the maximum voltage is not 4 volts, replace EGR valve. If maximum voltage is 4 volts, ensure voltage consistently increases and decreases as vacuum increases and decreases.
  13. If voltage does not increase and decrease with vacuum, replace EGR valve. If voltage does increase and decrease, reconnect hose No. 16 to EGR valve. Turn ignition off. Connect ECU Test Harness to ECU. (Scheme 69) Start engine and allow to idle. Measure voltage between ECU positive terminals C8 and negative terminals C12. If approximately 1.2 volts is not present, repair open in White/Black or Yellow wire between ECU terminal C8 and EGR lift sensor.
  14. If 1.2 volts are present, connect jumper between terminals A10 and A18. If engine did not stall, repair open in Pink wire between ECU terminal A11 and EGR control solenoid valve. If engine stalled, substitute a known good ECU. If condition goes away, replace original ECU.
  1. Turn ignition off. Remove CLOCK fuse (Prelude) in the under-hood relay box for 10 seconds to reset ECU. Turn ignition on. Verify if CHECK ENGINE light is on and if LED is flashing Code 13. If LED is flashing Code 13, go to next step. If LED is not flashing Code 13, problem is intermittent. Check connectors at PA sensor and related circuits.
  2. Turn ignition off. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Turn ignition on. Measure voltage between terminals C13 (positive) and C12 (negative). If about 5 volts are present, go to next step. If about 5 volts are not present, substitute a known good ECU and recheck. If condition is corrected, replace original ECU.
  3. Measure voltage between terminals C9 (positive) and C12 (negative). If about 3 volts are present, substitute a known good ECU and recheck. If condition is corrected, replace original ECU. If about 3 volts are not present, disconnect main wire harness from PA sensor. 4) Measure voltage between terminals C9 (positive) and C12 (negative). If about 5 volts are not present, repair short in Red wire between ECU terminal C9 and PA sensor. If about 5 volts are present, Measure voltage between White/Yellow (positive) and Green/White (negative) terminals.
  4. If about 5 volts are present, go to step 6). If about 5 volts are not present, measure voltage between White/Yellow terminal and body ground. If about 5 volts are present, repair open in Green/White wire between ECU terminal C12 and PA sensor. If about 5 volts are not present, repair open in White/(Yellow wire between ECU terminal C13 and PA sensor.
  5. Measure voltage between Red (positive) and Green/White (negative) terminals. If about 5 volts are present, replace PA sensor. If about 5 volts are not present, repair open in Red wire between ECU terminal C9 and PA sensor.
  1. Turn ignition off. Remove CLOCK fuse in the underhood relay box for 10 seconds to reset ECU. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 14. If LED is flashing Code 14, go to next step. If LED is not flashing Code 14, problem is intermittent. Check connectors at EACV and related circuits.
  2. Turn ignition off. Disconnect Electronic Air Control Valve (EACV) connector. Check resistance between the 2 connector terminals on valve.
  3. Resistance should be 8-15 ohms. If not within specification, replace EACV. If resistance is within specification, proceed to next step.
  4. Check for continuity to ground on each EACV connector terminal. If continuity exists, replace EACV. If no continuity exists, turn ignition on. Measure voltage between positive Yellow/Black wire terminal and negative Blue/Red wire terminals.
  5. Check for battery voltage. If no battery voltage exists, proceed to step 6). If battery voltage exists, disconnect connector from ECU and again check for battery voltage. If battery voltage still does not exist, substitute a known good ECU. If condition is corrected, replace original ECU. If battery voltage does exist, repair short in Blue/Red wire between ECU terminal A11 and EACV.
  6. If no battery voltage existed in step 5), measure voltage between ground and Yellow/Black (Prelude) wire terminal. If battery voltage now exists, proceed to step 7). If battery voltage still does not exist, repair open Yellow/Black wire between main relay and EACV.
  7. If battery voltage exists, turn ignition off. Reconnect EACV connector. Connect ECU Test Harness connector "A" to main wire harness side only. Turn ignition on. Measure voltage between connector positive terminals A11 and negative terminals A18. If voltage does not exist, repair open in Black/Blue (Prelude) wire between ECU terminal A11 and EACV.
  8. If battery voltage exists, connect and disconnect terminal A11 to A18. If EACV does not click when connector is connected and disconnected, replace EACV. If EACV clicks, substitute a known good ECU. If condition is corrected, replace original ECU.
  1. Turn off ignition. Reset ECU by removing CLOCK fuse in under-hood relay box for 10 seconds. Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 15. If LED is flashing Code 15, go to next step. If LED is not flashing Code 15, problem is intermittent. Check connector at distributor and related circuits.
  2. Turn ignition off. Disconnect 6-wire connector at ignitor. Turn ignition on. Measure voltage between ground and Black/Yellow wire terminal on wire harness side. If battery voltage is not present, repair open Black/Yellow wire between connector and ignition switch.
  3. If battery voltage is present, turn ignition off. Reconnect 2-wire or 6-wire connector. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Turn ignition on. Individually, measure voltage between negative terminal A18 and positive terminals B15 and B17.
  4. If battery voltage is present, substitute a known good ECU and retest. If condition is corrected, replace original ECU. If battery voltage is not present, go to step 6).
  5. Turn ignition off. Disconnect 6-wire ignitor connector and connectors from ECU side only. Check for continuity between White wires and ECU terminals B15 and B17 and ignitor. If continuity does not exist, repair as necessary. If continuity does exist, check for continuity between ground and White wires of 6-wire connector. If continuity exists, repair short to ground. If continuity does not exist, replace ignitor unit.
  1. Turn ignition off. Remove CLOCK fuse in the under-hood relay box for 10 seconds to reset ECU. Attempt to start engine. If engine does not start, go to step 3). Verify if CHECK ENGINE light is on and if LED is flashing Code 16. If LED is flashing Code 16, go to next step. If LED is not Hashing Code 16, problem is intermittent. Check connectors at injectors, injector resistor and related circuits. NOTE: On Prelude models w/2.0L engine, It may be necessary to crank engine for a minimum of 15 seconds to reset failure codes.
  2. Using a stethoscope, check for clicking sound at each injector while engine is idling. If all injectors click, substitute a known good ECU. If condition is corrected, replace original ECU.
  3. Turn ignition off. If engine does not start, check resistance of all injectors. If engine does start, check resistance of injectors which did not click. If resistance value is not 1.5-2.5 ohms, replace injector(s). If resistance values are within specification, turn ignition on. Measure voltage between ground and Red/Black wire at injector.
  4. If battery voltage is not present, go to step 6). If battery voltage is present, reconnect injector connector(s). Turn ignition off. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Turn ignition on. Measure voltage between negative terminal A18 and the following positive terminals. Injector No. 1 - A1 Injector No. 2 - A3 Injector No. 3 - A5 Injector No. 4 - A7
  5. If battery voltage is not present, repair open in wire A1 (injector 1), A3 (injector 2), A5 (injector 3) or A7 (injector 4) between ECU and injector. If battery voltage is present, substitute a known good ECU. If condition is corrected, replace original ECU.
  6. Turn ignition off. Disconnect injector resistor 6-wire connector. Turn ignition on. Measure voltage between ground and Yellow/Black wire terminal. If battery voltage is present, repair open in Red/Black wire between 2-wire connector and injector resistor. If wire is good, replace injector resistor. If battery voltage is not present, repair open in Yellow/Black wire between injector resistor and main relay.

Engine Will Not Start

  1. Remove HAZARD fuse in main fuse box for 10 seconds to reset ECU. Crank engine for at least 15 seconds to reproduce trouble code in ECU memory. Verify if CHECK ENGINE light is on and if trouble code(s) is present. If light is not on and trouble codes are not present, perform SPARK test in «BASIC TESTING - FUEL INJECTED»(/honda/prelude/iii-1989-1992/remont/testing-diagnostics/#engine-controls-basic-testing-fuel-injected) article.
  2. If CHECK ENGINE light is on and LED is flashing Code 16, turn ignition off. Disconnect 2-wire connector from auxiliary injector. Check resistance between the injector terminals. Resistance should be 6-10 ohms. If resistance is not 6-10 ohms, replace auxiliary injector.
  3. If resistance was okay, turn ignition switch on. Measure voltage between auxiliary injector connector Yellow wire and ground. If about 10 volts is present, go to step 4). If about 10 volts are not present, repair open or short in Yellow wire between auxiliary injector and ECU terminals A1 and A3. If wire is okay, substitute a known good ECU and retest. If specified voltage is now available, replace original ECU.
  4. Disconnect 2-wire connector from main injector. Measure voltage between main injector's Red wire and ground. If about 10 volts is present, go to step 5). If about 10 volts are not present, repair open or short in Red wire between main injector and ECU terminals A5 and A7. If wire is okay, substitute a known good ECU and retest. If specified voltage is now present, replace original ECU.
  5. Turn ignition off. Connect voltmeter positive lead to Yellow/Black wire of auxiliary injector and voltmeter negative lead to ground. Turn ignition on. If battery voltage is present for 2 seconds, substitute a known good ECU and retest. If specified voltage is now present, replace original ECU. If battery voltage is not present for 2 seconds, go to step 6).
  6. Turn ignition off. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Jumper ECU terminals A18, A12 and A14 to each other. Turn ignition on. Check for battery voltage at Yellow/ Black wire of auxiliary injector connector.
  7. If battery voltage is not present, check and repair open in Black/Yellow wire between auxiliary injector and main relay or Green/Black wire between main relay and ECU terminals A12 and A14. If wires are okay, replace main relay.
  8. If battery voltage was present from step 6), repair Black wire between ground on thermostat housing and ECU terminals A2 and A4. If wire is okay, substitute a known good ECU and retest. If specified voltage is now present, replace original ECU.
  1. Turn ignition off. Reset ECU by removing CLOCK fuse in under-hood relay box for 10 seconds. Road test vehicle. With transmission in 2nd gear, accelerate to 3500 RPM, then decelerate to 1500 RPM with throttle fully closed. Verify if CHECK ENGINE light is on and if LED is flashing Code 17. If LED is flashing Code 17, go to next step. If LED is not flashing Code 17, problem is intermittent. Check connectors and related circuits.
  2. Block rear wheels and set parking brake. Raise front of vehicle and support with stands. Connect ECU Test Harness between ECU and ECU connector. (Scheme 69) Turn ignition on.
  3. Slowly rotate left front wheel and measure voltage between positive terminal B16 and negative terminal A18. If voltmeter does not pulse, go to step 4). If voltmeter pulses from 0-5 volts, substitute a known good ECU and recheck. If specified voltage is now present, replace original ECU.
  4. Repair open or short in White/Blue wire between ECU and VSS. If wire is okay, replace VSS sensor. If voltage is still not as specified, substitute a known good ECU and recheck. If specified voltage is now present, replace original ECU.

Scheme 71

Scheme 71: WIRING DIAGRAM
Scheme 71: WIRING DIAGRAM

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.

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