Electronic Control System Honda Accord III

The Electronic Control Unit (ECU) receives signals (data) from various sensors. The ECU processes input data and sends output signals to various control devices. This allows for precise control of air/fuel mixture and idle speed under all operating conditions.

The ECU is the main controlling device of the electronic control system. The basic injector duration is read from calibration tables built into ECU internal memory. The ECU modifies the basic injector duration according to input signals from various sensors to obtain the final injector duration. This allows the ECU to obtain optimum injector pulse.

The ECU also controls cold start system, electric fuel pump and fuel cut-off systems. The ECU contains a fail-safe system to monitor sensors and detect any abnormality in ECU itself. This provides safe driving even if one or more of the sensors are faulty or ECU malfunctions.

The ECU has a self-diagnostic capability to help diagnose problems. This system uses a dash mounted PGM-FI or Check Engine warning light and one ECU mounted self-diagnostic LED. The PGM-FI warning light will glow for 2 seconds when ignition is turned on. The ECU is mounted below passenger seat.

Note. For additional information on fuel control portion of this system, see PGM-FI SYSTEM article in FUEL SYSTEMS section.

INPUT SIGNALS

Computer furnishes input sensors with a reference voltage (5 volts). This voltage signal is then modified by the resistance value of the sensors in each circuit. Some sensors are simple mechanical resistors, while others are temperature sensitive resistors (thermistors). ECU monitors either reference line or return signal to determine status of each sensor. Not all input signals are obtained from sensors. Some input signals are simply monitored circuits which either produce a voltage of their own (O2 and pick-up coils or already have a voltage signal present.

Atmospheric Pressure Sensor (PA)

The PA sensor converts atmospheric pressure into voltage signals and sends them to ECU.

Battery Voltage Signal

ECU uses the battery voltage signal (alternator FR terminal) to compensate for low voltage conditions which result in injector lag. ECU compensates by increasing injector opening time.

Crank Angle Sensors

The crank angle sensor consists of a combination TDC/CYL sensor mounted in the distributor housing. (Scheme 42) This sensor furnishes 2 separate input signals to the ECU. The ECU uses the CYL signal to help determine No. 1 cylinder position as a base for sequential fuel injection. The ECU uses the TDC signal to determine injection timing for each cylinder. This sensor also furnishes an RPM signal to ECU. (Scheme 42)

TDC/CYL Sensor. Scheme 42

Coolant Temperature Sensor (TW)

The TW sensor uses a temperature sensitive resistor (thermistor) to measure differences in coolant temperature. Resistance of thermistor decreases with a rise in coolant temperature.

EGR Lift Sensor

The ECU contains ideal EGR lift specifications for varying operating conditions in its internal memory. EGR lift sensor senses EGR valve position and relays information to ECU. ECU uses this information, along with other sensor input, to determine regulation of EGR control solenoid valve.

Intake Air Temperature Sensor (TA)

The TA sensor is a thermistor located in the intake manifold. It acts much like the coolant temperature sensor but with a reduced thermal capacity for quicker responses.

Manifold Air Pressure Sensor (MAP)

The MAP sensor converts manifold air pressure readings into electrical voltage signals and sends the signals to ECU.

Oxygen Sensor

The oxygen sensor is mounted in the exhaust manifold where it is exposed to exhaust gases as they exit the combustion chamber. Sensor detects oxygen content of exhaust gas and produces a voltage signal proportional to that content for use by the ECU.

Rich air/fuel ratios will cause oxygen sensor to produce a high signal voltage (up to 1.0 volt), while lean air/fuel ratios will cause sensor to produce a low signal voltage (as low as .1 volt). The ECU receives these input signals and varies fuel injector duration (on time) to maintain proper air/fuel ratios during most operating modes.

Note. Two oxygen sensors are used, one in each exhaust manifold.

Throttle Position Angle Sensor

This sensor is a mechanical variable resistor (potentiometer) connected to throttle shaft. Throttle position sensor varies voltage signal to ECU as throttle angle changes.

Other input signals which may be used on some or all models include signals from A/C clutch, brake switch, clutch switch, cranking signal (fused starter switch), vehicle speed sensor, power steering pressure switch and/or gear position switch(es).

By-Pass Control Solenoids

Two air intake paths are provided in intake manifold. This allows ECU to select path length most favorable (power/performance) for a given engine speed. These air paths are selected by ECU based upon sensor input signals. ECU controls by-pass valves in intake manifold through use of 2 by-pass control solenoids and a by-pass valve control diaphragm. See PGM-FI SYSTEM article in FUEL SYSTEMS section.

Electronic Air Control Valve (EACV)

All models are equipped with an Electronic Air Control Valve. When idle speed is reduced due to electrical or other loads on engine, ECU opens this valve to by-pass additional air into intake manifold. This additional air will allow idle speed to increase to maintain normal idle.

After coolant temperature has reach 104°F (40°C), this valve lowers fast idle speed in steps during engine warm-up. To prevent erratic running after engine first fires, valve is opened during cranking and immediately after starting which by-passes additional air into intake manifold.

Exhaust Gas Recirculation (EGR) Control Solenoid

ECU controls ground circuit to EGR solenoid to regulate flow of recirculated exhaust gases into intake system. Accord models also utilize an EGR valve lift sensor. This allows ECU to not only control EGR function, but to monitor it and set a trouble code (code 12) if a malfunction occurs.

Electric Fuel Pump

The fuel pump is a direct drive type mounted in fuel tank. When ignition is first turned on, ECU supplies a ground circuit for main relay for about 2 seconds. When relay is energized, power is transmitted to fuel pump. When an RPM signal is received by ECU (cranking or running), ECU provides a constant ground circuit for main relay.

Fast Idle Valve

A higher idle speed is needed on all models to prevent erratic running during engine warm-up. This is accomplished through use of a thermowax fast idle valve. When thermowax valve is less than 85°F (30°C), valve is open. When valve is open, additional air is allowed to by-pass throttle valve into intake manifold. When thermowax is hot, valve is closed. This operation is dependent solely upon coolant temperature.

Fuel Injector

Battery voltage for injector is supplied from main relay and then passes through injector resistor before reaching injectors. Injectors are energized when ECU supplies a ground circuit for individual injectors. Because plunger valve lift and fuel pressure are constant, air/fuel ratio is determined solely by length of time that injector is open.

Note. Accord models have injectors located in intake manifold, one injector for each cylinder.

Ignition Timing

On Accord models, ignitor inside distributor triggers ignition coil based upon its own pick-up coil signals. This trigger signal is further modified by both vacuum and centrifugal advance mechanisms. The vacuum advance mechanism consists of a dual-diaphragm which operates on manifold vacuum. Vacuum to the outside diaphragm is controlled by an ECU-regulated vacuum solenoid. This solenoid will pass vacuum to outside diaphragm when vehicle is cold. This allows additional advance to improve cold engine performance.

Main Relay

One half of main relay is used by ECU to power electric fuel pump. ECU provides a ground for this part of relay when ignition is first turned on (2 seconds), or when an RPM signal is received by ECU (Cranking or running). The second half of the main relay provides power from ignition for the ECU, injectors and power for the fuel pump part of relay.

Purge Control Solenoid

Purging evaporative emissions from charcoal canister is controlled by ECU using purge control solenoid. When solenoid is energized, manifold vacuum passes through solenoid to open canister purge control valve diaphragm located on top of canister. Ported vacuum is then used to purge canister.

Vacuum Control Solenoid Valve

Vacuum to the outside control solenoid. This solenoid will pass vacuum to outside diaphragm when vehicle is cold, supplying additional advance to improve cold engine performance.

Other control functions which may be used on some or all models include the PGM-FI or Check Engine warning light, economy driving indicator light and A/C clutch relay.

TROUBLE SHOOTING

Note. Observe PGM-FI or Check Engine warning light. If light is on and no codes are flashed by LED on ECU, this indicates that backup system is in operation. see LED DOES NOT FLASH under CODE 0, NO CODES in TESTING section of this article.

ENGINE WON'T START

Check spark, fuel supply and EACV.

DIFFICULT COLD START

Check coolant temperature sensor, TDC sensor and all other idle controls.

FAST IDLE OUT OF SPECIFICATION

Check idle controls, coolant temperature sensor, throttle position sensor, TDC sensor, intake air temperature sensor and atmospheric pressure sensor.

ROUGH IDLE WHEN WARM

Check EACV, MAP sensor, oxygen sensor, crank angle sensor, throttle position sensor, intake air temperature sensor, atmospheric pressure sensor and EGR and other emission control systems.

IDLE RPM HIGH WHEN WARM

Check EACV and other idle controls. Check MAP sensor, atmospheric pressure sensor, air intake system and emission systems.

IDLE RPM LOW WHEN WARM

Check EACV, air intake system, MAP sensor and other idle controls.

STALLING AFTER WARM-UP

Check EACV, air intake system, MAP sensor, crank angle sensor, coolant temperature sensor, throttle position sensor, other idle controls, fuel supply and EGR control system.

STALLING DURING WARM-UP

Check EGR control system, EACV, MAP sensor, throttle position sensor, crank angle sensor, vehicle speed sensor, air intake and fuel supply.

MISFIRE OR ROUGH OPERATION

Using a stethoscope, check each injector for clicking at idle. Check fuel supply, MAP sensor, oxygen sensor, crank angle sensor, throttle position sensor, ignition output signal, EGR system and vehicle speed sensor.

EMISSION TEST FAILURE

Check MAP sensor, oxygen sensor, all emission control systems, crank angle sensor and coolant temperature sensor.

LACK OF POWER

Check for dragging/binding brakes. Check fuel supply, MAP sensor, crank angle sensor, coolant temperature sensor, atmospheric pressure sensor, vehicle speed sensor, air intake system and control system.

TESTING

Note. Before starting testing, ensure engine is in good mechanical condition and adjusted to specifications.

On all models, an LED is located on ECU under driver's side seat for self-diagnostic codes. LED is used to read codes set due to component failure. See appropriate LED CODES table in this article. To obtain codes, turn ignition switch to the "ON" position and count flashes of LED on ECU.

Note. If unlisted codes are flashed by ECU LED, clear codes and recheck. If code still appears, substitute a known good ECU. If condition is rectified, replace original ECU.

ECU Terminal I.D. & System Checker Harness Installation. Scheme 43

On all models, System Checker Harness (07999-PD60000A ) is needed to test components. (Scheme 43) An Inspection Harness (07GMJ ML80100 ) is needed for testing specific 3-wire sensors. Both of these devices function as breakout boxes to access pin voltage signals while component is either in or out of circuit.

To reset ECU, remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU.

LED CODE

No PGM-FI Warning Light

1. Turn ignition on. If oil pressure light is on, go to step 2). If light is off, inspect fuse No. 2. If fuse is okay, repair open circuit in Yellow wire between fuse and combination meter.
2. Turn ignition off. Connect system checker harness between ECU and connector. Connect terminal B6 to ground. Turn ignition on. If warning light is now on, go to step 3). If light is off, replace warning light bulb or repair open in wire between ECU terminal B6 and combination meter.
3. Individually, connect terminal A2 and then terminal A4 to terminal B6. If warning light fails to illuminate, repair open in Black A2 or A4 wires between ECU and ground.
4. If warning light illuminated in step 3), substitute a known good ECU. If condition is rectified, replace original ECU.

PGM-FI Warning Light On, LED Does Not Flash Codes

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 the sensor which caused LED to go out when unplugged.
2. Reconnect all connectors. Disconnect the 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 system checker harness between ECU and ECU harness. Disconnect "C" connector from ECU, not main harness. Check for 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 "C" connector. Disconnect "B" connector from ECU only, not main harness. Turn ignition on. If LED is lit, repair short to ground in Green/Red wire between ECU terminal B6 and combination meter. If LED is not lit, one at a time, connect terminal B6 to terminal A16 and then to terminal A18. If LED illuminates, go to step 5). If not, repair individual ground connections which did not make light come on (A118 or A16).
5. Measure voltage between terminal (A15 (pos.) and A18 (neg.). If battery voltage is not present, repair open Yellow//White 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 rectified, replace original ECU.

Code 1 &/or Code 2 - Oxygen Sensor

1. Turn off ignition. Reset ECU by removing No. 11 fuse in the under-hood relay box for 10 seconds. Start engine. Check fuel pressure at fuel filter. See appropriate FUEL INJECTION article in FUEL SYSTEMS section. Repair fuel system if not within specifications. If fuel pressure is within specifications, 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. Check if PGM-FI or Check Engine Warning Light is on. If not on, problem is intermittent. Test drive and check light again.
3. If light is on, disconnect indicated oxygen sensor connector. Attach voltmeter to vehicle ground and oxygen 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 engine off and attach system checker harness between ECU and ECU connector. Using a voltmeter, connect negative lead to connector terminal A18.
6. For oxygen sensor A, attach positive voltmeter lead to connector terminal C16 and attach to connector terminal B11 for oxygen sensor B.
7. Start engine and warm to operating temperature. Momentarily open throttle wide open, then close throttle. Voltage at wide open throttle should be greater than .6 volt, and less than .4 volt at closed throttle. If not within specifications, repair wire between ECU and oxygen sensor. If within specifications, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 3, MAP SENSOR

1. Turn ignition off. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Connect test harness between MAP sensor and sensor harness. Turn ignition on. Measure voltage between Red (pos.) and Green (neg.) terminals. If reading is about 5 volts, go to step 4). If not, measure voltage between Red (pos.) terminal and ground. If voltage is still not 5 volts, go to step 3). If voltage is about 5 volts, repair open in Green/White wire between ECU terminal C14 and MAP sensor.
3. Turn ignition off. Connect system checker harness between ECU and ECU harness. Measure voltage between terminal C15 (pos.) and C14 (neg.) with ignition on. If voltage reading is about 5 volts, repair open Red/White wire between ECU terminal C15 and MAP sensor. If voltage is not about 5 volts, substitute a known good ECU. If condition is rectified, replace original ECU.
4. Measure voltage between White (pos.) and Green (neg.) terminals. If reading is not about 3 volts, replace MAP sensor or repair short in White/Blue wire between ECU terminal C11 and MAP sensor.
5. If measured voltage is about 3 volts, turn ignition off. Connect system checker harness between ECU and ECU connectors. Turn ignition on. Measure voltage between terminals C11 (pos.) and C14 (neg.). If there is not about 3 volts present, repair open White/Blue wire between ECU terminal C11 and MAP sensor.
6. If there are about 3 volts present, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 5, MAP SENSOR

1. Turn ignition off. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Using a "T" fitting, connect a handheld vacuum pump/gauge into vacuum hose between throttle body and MAP sensor. Start engine. If vacuum is not present, repair as necessary. If vacuum is present and holds, turn ignition off.
3. Connect inspection harness between MAP sensor and harness. Turn ignition on. Measure voltage between White (pos.) terminal and Green (neg.) terminal. If reading is not about 3 volts, replace MAP sensor. If voltage reading is about 3 volts, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 6, COOLANT (TW) SENSOR

1. Turn ignition off. Remove clock No. 11 fuse in the under hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, warm engine to normal operating temperature (cooling fan comes on). 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, measure voltage between ground and Yellow/Green wire of sensor harness. If reading is not about 5 volts, go to step 5). If reading is about 5 volts, measure voltage between Yellow/Green (pos.) and Green/White wires of connector harness.
4. If voltage is not about 5 volts, repair open Green/White (neg.) wire between ECU terminal C12 and sensor. If voltage reading is correct, substitute a known good ECU. If condition is rectified, replace original ECU.
5. If voltage between ground and Yellow/Green wire of sensor harness did not read 5 volts in step 3), turn ignition off. Connect system checker harness between ECU and ECU connector. Turn ignition on. measure voltage between terminals C6 (pos.) and C12 (neg.) if voltage reading is about 5 volts, repair open Yellow/Green wire between ECU terminal C6 and TW sensor.
6. If reading is not about 5 volts, disconnect "C" connector from main wire harness only, not the ECU. Measure voltage between terminals C6 (pos.) and C12 (neg.). If reading is not about 5 volts, go to next step. If voltage reading is about 5 volts, repair short in Yellow/Green wire between ECU terminal C6 and sensor.
7. If voltage reading is still not about 5 volts, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 7, THROTTLE ANGLE SENSOR

1. Turn off ignition. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Disconnect 3-wire connector at throttle position sensor. Turn ignition on. Measure voltage between Yellow/White (pos.) and Green/White (neg.) terminals. If voltage is not about 5 volts, go to step 5). If voltage is about 5 volts, turn ignition off. Reconnect sensor connector. Connect system checker harness between ECU and ECU connector.
3. Turn ignition on. Measure voltage between terminals C7 (pos.) and C12 (neg.). 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 sensor does not respond as indicated in step 3), replace throttle sensor or repair open or short in Red/Yellow wire between ECU terminal C7 and throttle sensor. If throttle sensor responds as indicated, substitute a known good ECU. If condition is rectified, replace original ECU.
5. If voltage reading between Yellow/White (pos.) and Green/White (neg.) 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 about 5 volts is not present between ground and Yellow/White wire, turn ignition off.
6. Connect system checker harness between ECU and ECU connector. Turn ignition on. Measure voltage between terminals C13 (pos.) and C12 (neg.). If voltage is still not about 5 volts, go to next step. If voltage is about 5 volts, repair open Yellow/White wire between ECU terminal C13 and throttle sensor.
7. Substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 8, CYL SENSOR

1. Turn ignition off. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Disconnect sensor connector at distributor. Using an ohmmeter, measure resistance between Orange/Blue and White/Blue terminals. If reading is not 650-850 ohms, replace crank angle sensor. 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 crank angle sensor. If no continuity exists, proceed to next step.
4. Reconnect sensor connector. Attach system checker harness to main wire harness only, not to ECU. Using an ohmmeter, check resistance between connector C3 and C4 terminals. Resistance should be 650-850 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, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 9, CRK/CYL SENSOR

1. Turn ignition off. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning 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 near distributor. Measure resistance between White and Orange wire terminals at sensor. If reading is not 650-850, replace sensor. If reading is within specification, proceed to next step.
3. Check continuity between ground and White wire terminal. Check continuity between ground and Orange wire terminal. If continuity exists, sensor is shorted to ground. Replace sensor. If no continuity exists, proceed to next step.
4. Reconnect sensor connector. Attach system checker harness to main wire harness only, not to ECU. Check resistance between connector terminals C1 and C2. Resistance should be 650-850 ohms.
5. If resistance not within specification, repair open in Orange and/or White wire. If resistance is within specification, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 10, AIR TEMPERATURE (TA) SENSOR

1. Turn off ignition. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Measure resistance across TA sensor terminals. If reading is not 1000-4000 ohms, replace sensor. If resistance is within specification, measure voltage between ground and White/Red wire terminal. 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 same wire (pos.) and Green/White (neg.) wire terminal. If voltage is not about 5 volts, repair open in Green/White between ECU terminal C12 and sensor. If reading is about 5 volts, substitute a known good ECU. If condition is rectified, replace original ECU.
4. If voltage in step 2) was not about 5 volts, turn ignition off. Connect system checker harness between ECU and ECU connector. Turn ignition on. Measure voltage between terminals C5 (pos.) and C12 (neg.). If voltage reading is about 5 volts, repair open in White/Red wire between ECU terminal C5 and sensor.
5. If reading was not about 5 volts, disconnect "C" connector from the main wire harness only, not the ECU. Measure voltage between terminals C5 (pos.) and C12 (neg.). If voltage reading is about 5 volts, repair short in White/Red or Red/Yellow wire between ECU terminal C5 and sensor.
6. If voltage is not about 5 volts, substitute a known good ECU. If voltage is now correct, replace original ECU.

CODE 12, EGR SYSTEM

1. Check harness and connections between EGR valve and ECU. Warm engine to normal operating temperature (cooling fan on). Disconnect vacuum hose from EGR valve. Using a hand-held vacuum pump, apply vacuum to EGR valve. If vacuum does not hold, and engine does not stall, replace faulty EGR valve or clean blocked EGR passages.
2. If vacuum held and engine stalled in step 1), restart engine. Open control box. Verify vacuum from intake manifold to CVC valve. Repair as necessary. Reconnect manifold vacuum hose. Disconnect vacuum hose between CVC valve and air chamber. Connect vacuum gauge and check for about 8 in. Hg.
3. If reading is not about 8 in. Hg, replace CVC valve. If vacuum is correct, reconnect vacuum hose. Install vacuum gauge at EGR valve hose. Disconnect electrical connector from control box. Jumper voltage to Black/Yellow wire terminal of box and ground to Red wire terminal of box. Reading at EGR valve hose should now be about 8 in. Hg.
4. If vacuum reading is not correct, replace EGR control solenoid. If reading is correct, measure voltage from ground to Black/Yellow wire of control box harness connector. If battery voltage is not present, repair open in Black/Yellow wire between No. 1 fuse and control box harness connector.
5. If battery voltage is present, turn ignition off. Connect test harness between EGR lift sensor and sensor harness connector. Turn ignition on. Measure voltage between Red (pos.) and Green (neg.) terminals. If voltage is about 5 volts, go to step 7). If voltage is not about 5 volts, measure voltage between ground and Red terminal. If voltage is now about 5 volts, repair open in Green/White wire between ECU terminal C12 and sensor.
6. If voltage is not about 5 volts, turn ignition off. Connect system checker harness between ECU and ECU connector. Measure voltage between terminals C13 (pos.) and C12 (neg.). If voltage is now about 5 volts, repair open in Yellow/White wire between ECU terminal C13 and sensor. If voltage is not about 5 volts, substitute a known good ECU. If condition is rectified, replace original ECU.
7. Measure voltage between White (pos.) and Green (neg.) terminals. If voltage reading is not about one volt, replace EGR valve or repair short in Red wire between ECU terminal A10 and EGR control solenoid. If about one volt is measured, turn ignition off. Connect system checker harness between ECU and ECU connector.
8. Turn ignition on. Measure voltage between terminals C8 (pos.) and C12 (eng.). If voltage is not about one volt, repair open in Yellow wire between ECU terminal C8 and sensor. If voltage is about one volt, disconnect "A" connector from ECU only, not from main harness.
9. Measure voltage between terminals A10 (pos.) and A18 (neg.). If battery voltage is not present, repair open or short in Red wire between ECU terminal A10 and EGR control solenoid. If battery voltage is present, substitute a known good ECU. If condition is rectified, replace original ECU.

CODE 13, ATMOSPHERIC (PA) SENSOR

1. Turn off ignition. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, turn ignition off. Connect system checker harness between ECU and ECU connector. Turn ignition on. Measure voltage between terminals C13 (pos.) and C12 (neg.). If about 5 volts is red, go to step 3). If not, substitute a known good ECU. If correct voltage is now indicated, replace original ECU.
3. Measure voltage between terminals C9 (pos.) and C12 (neg.). If about 3 volts is not present, go to step 4). If about 3 volts is present, substitute a known good ECU. If condition is rectified, replace original ECU.
4. Disconnect connector from atmospheric pressure sensor. Measure voltage between terminals C9 (pos.) and C12 (neg.) on harness side. If about 5 volts is indicated, go to step 5). If about 5 volts is not indicated, repair short in Red wire between ECU terminal C9 and sensor.
5. Measure voltage between Yellow/White and Green/White (neg.) wires. If reading is not about 5 volts, go to step 6). If about 5 volts is present, measure voltage between Red and Green/White (neg.) terminals. If about 5 volts is not read, repair open Red or Red/White wire between ECU terminal C9 and sensor. If about 5 volts is red, replace sensor.
6. Measure voltage between ground and Yellow/White wire of harness. If about 5 volts is not present, repair open in White/Yellow or Yellow/White wire between ECU terminal C13 and sensor. If about 5 volts is present, repair open Green/White wire between ECU terminal C12 and sensor.

CODE 14, IDLE CONTROL SYSTEM EACV

1. Turn off ignition. Remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
2. If light is on, 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. Connect voltmeter between Black/Yellow (pos.) and Black/Blue (neg.) 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 rectified, replace original ECU. If battery voltage does exist, repair short in Black/Blue wire between ECU terminal A11 and EACV.
6. If no battery voltage existed in step 5), measure voltage between ground and Black/Yellow wire terminal. If battery voltage now exists, proceed to step 7). If battery voltage still does not exists, repair open Black/Yellow wire between fuse No. 1 and EACV.
7. If battery voltage exists, turn ignition off. Reconnect EACV connector. Connect system checker harness "A" connector to main wire harness only, not ECU. Turn ignition on. Using a voltmeter, measure voltage between connector terminals A11 (pos.) and A18 (neg.). If voltage does not exist, repair open in 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 EAVC clicks, substitute a known good ECU. If condition is rectified, replace original ECU.

Accord Wiring Schematic. Scheme 44