Electronic Engine Control System Acura Integra I

DESCRIPTION & OPERATION

The Electronic Control Unit (ECU) receives signals from various sensors. ECU computes the signals and sends output signals to various control devices. The ECU is the main controlling device of the electronic control system. The ECU is mounted below passenger seat.

The ECU contains memories for the basic injector durations at various engine RPM and Manifold Absolute Pressures (MAP). The basic injector duration is read out of the memory of the ECU. The ECU modifies the basic injector duration according to input signals from various sensors to obtain the final injector duration.

The ECU 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. This provides safe driving even if one or more of the sensors are faulty or the ECU malfunctions.

There are several sensors used to provide operating information to the ECU. They include Top Dead Center (TDC) sensor, Crank/Cylinder (CRK/CYL) sensors, Manifold Absolute Pressure (MAP) sensor, Atmospheric Pressure (PA) sensor, coolant temperature sensor, intake air temperature sensor, throttle angle sensor, front and rear oxygen sensors, Idle Mixture Adjuster (IMA) sensor and starter switch.

Note. TDC sensor and CRK/CYL sensor vary depending on vehicle application.

The electronic control system has a self-diagnostic function to help diagnose problems. This system uses a dash mounted PGM-FI warning light and one or 2 ECU mounted self-diagnostic lights. All models use a Red LED light on ECU for system failure code. The PGM-FI warning light will glow for 2 seconds when ignition switch is turned to the "ON" position.

Crank Angle Sensors

The crank angle sensor consists of a CYL sensor and a TDC sensor mounted on the camshaft. Integra model utilizes a CYL rotor and CYL pick-up with a TDC rotor and TDC pick-up, which is mounted to camshaft. (Scheme 15)

The CYL sensor detects position of No. 1 cylinder as a base for sequential injection. The TDC sensor determines the injection of each cylinder and supplies the engine RPM to the ECU.

View of Integra Crank Angle Sensor. Scheme 15

Manifold Air Pressure (MAP) Sensor

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

Atmospheric Pressure (PA) Sensor

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

Coolant Temperature (TW) Sensor

The TW sensor uses a temperature dependent resistor (thermistor) to measure differences in coolant temperature. Basic discharge read out is by signals sent from TW sensor through ECU. Resistance of thermistor decreases with a rise in coolant temperature.

Intake Air Temperature (TA) Sensor

The TA sensor is a thermistor and is placed in intake manifold. It acts much like coolant temperature sensor but with a reduced thermal capacity for quicker responses. Resistance of thermistor decreases as intake air temperature increases.

Throttle Angle Sensor

This sensor is essentially a variable resistor (potentiometer). Connected to throttle shaft, throttle angle sensor varies voltage signal to ECU, as throttle angle changes.

Oxygen Sensor

The oxygen sensor, detects oxygen content of exhaust gas and signals the ECU. ECU receives the input signals and varies duration during fuel injection. This maintains stoichiometric air/fuel ratio. The oxygen sensor is mounted in exhaust manifold.

Ignition Timing Adjuster (ITA)

The Ignition Timing Adjuster (ITA), is electrically connected to MAP sensor, throttle angle sensor, PA sensor, EGR valve lift sensor and ECU. The ITA allows electronic ignition advance to be set to 15 degrees BTDC at idle.

Throttle Body

Throttle body is a single barrel, side-draft type. The 2-barrel type has the primary air horn at the top. Lower portion of throttle body is heated by engine coolant. Idle adjusting screw and the canister/purge port are located on top of throttle body. A dashpot is used to prevent sudden closing of throttle during gear shifting.

Electronic Idle Control Solenoid Valve (EICV)

The ECU controls electrical current to EICV and maintains correct idle speed. The EICV is activated when the engine is cold, A/C is on, transmission is in gear (A/T only), power steering oil pressure is high, and alternator is charging.

Fast Idle Control Solenoid Valve

To prevent erratic running during engine warm-up, a higher idle speed is needed. When engine temperature is cold, this valve opens to by-pass additional air into intake manifold. This operation is dependent upon coolant temperature and atmospheric pressure.

ECU Connector Identification & Location. Scheme 16

ENGINE WON'T START

Check spark, fuel supply, ECU and crank angle sensor. Test component and repair as necessary.

DIFFICULT COLD START

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check coolant temperature sensor, electronic idle control valve and all other idle controls.

FAST IDLE OUT OF SPECIFICATIONS

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check idle controls, coolant temperature sensor, throttle angle sensor, TDC sensor, intake air temperature sensor and atmospheric pressure sensor.

ROUGH IDLE WHEN WARM

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check electronic idle control valve, MAP sensor, oxygen sensor, throttle angle sensor, intake air temperature sensor, atmospheric pressure sensor and EGR control system.

IDLE RPM HIGH WHEN WARM

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check idle controls and air intake system.

IDLE RPM LOW WHEN WARM

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check electronic idle control valve, other idle controls and air intake system.

STALLING DURING WARM UP

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check electronic idle control valve, air intake system, oxygen sensor, coolant temperature sensor, throttle angle sensor, other idle controls, fuel supply and EGR control system.

STALLING AFTER WARM UP

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check EGR control system, MAP sensor, throttle angle sensor, electronic idle control valve and fuel supply.

MISFIRE OR ROUGH OPERATION

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check fuel supply, MAP sensor, oxygen sensor, throttle angle sensor, TDC sensor and vehicle speed sensor (if equipped).

EMISSION TEST FAILURE

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check MAP sensor, oxygen sensor, ERG control system and all other emission controls.

LACK OF POWER

Check if PGM-FI light and Red LED light is on. This indicates that back-up system is in operation. Replace ECU with one known to be good and recheck. Check fuel supply, emission controls, MAP sensor, air intake system and EGR control system.

TESTING

Note. Before starting testing or trouble shooting, ensure engine is set to specifications.

SELF-DIAGNOSTIC CODES

On Acura models a System Checker Harness (07999-PD60000A) is needed to test components. To reset ECU, on Integra models, remove hazard fuse at battery terminal for 10 seconds.

A Red LED light is located on ECU for self-diagnosis codes. Some Models also have a Yellow LED light which is for idle speed adjustment and is not related to trouble shooting codes. The Red LED light is for codes set at component failure. See appropriate LED CODES table in this article. To obtain ECU codes, turn ignition switch to the "ON" position and watch ECU Red LED light.

INTEGRA LED CODES

CODE 1 & CODE 2 - OXYGEN SENSOR

1. Turn off ignition and reset ECU. Remove hazard fuse at battery terminal for 10 seconds.
2. Bring engine to operating temperature (cooling fan on). Hold engine at 1500-2000 RPM for 10 minutes, without closing throttle completely during this time. Check if PGM-FI light is on. If not on, test drive and check light again.
3. If light is on, check fuel pressure at fuel filter. See appropriate FUEL INJECTION article in this section. Repair fuel system if not within specifications. If fuel pressure is within specifications, proceed to next step.
4. Disconnect oxygen sensor connector. Attach voltmeter to vehicle ground and connector. With engine at normal operating temperature, open throttle wide open then close throttle.
5. Voltage at wide open throttle should be above .6 volt and below .4 volt at full closed throttle. If not within specifications, replace oxygen sensor. If voltage is within specifications, proceed to next step.
6. Turn engine off and attach system checker harness between ECU and connector. Using a voltmeter, connect negative terminal to connector terminal No. A18. Attach positive terminal to connector terminal No. C16.
7. Start engine and warm to operating temperature. Open throttle wide open then close throttle. Voltage at wide open throttle should be above .6 volt and below .4 volt at full closed throttle. If not within specifications, repair wire between ECU and oxygen sensor. If within specifications, proceed to next step.
8. Install a known good ECU and recheck system. If failed system is now corrected, replace ECU.

Code Zero, ECU Test Chart, Integra (1 of 2). Scheme 17

Code Zero, ECU Test Chart, Integra (2 of 2). Scheme 18

MAP Sensor Output Voltage Graph, Integra. Scheme 19

Code 3, MAP Sensor Test Chart, Integra (1 of 2). Scheme 20

Code 3, MAP Sensor Test Chart, Integra (2 of 2). Scheme 21

Code 5, MAP Sensor Test Chart, Integra (1 of 2). Scheme 22

Code 5, MAP Sensor Test Chart, Integra (2 of 2). Scheme 23

Code 6, TW Sensor Test Chart, Integra (1 of 2). Scheme 24

Code 6, TW Sensor Test Chart, Integra (2 of 2). Scheme 25

Code 7, Throttle Angle Sensor Chart, Integra (1 of 2). Scheme 26

Code 7, Throttle Angle Sensor Chart, Integra (2 of 2). Scheme 27

CODE 8 - TDC SENSOR

1. Turn ignition off. Disconnect hazard fuse at battery positive terminal for 10 seconds to reset ECU. Start engine and check for PGM-FI warning light on or off. If light is off, test drive and check again.
2. If light is on, turn engine off. Disconnect sensor connector nearest sensor. Measure resistance between Brown and Blue terminal. If ohm reading is not 650-850 ohms, replace sensor. If ohm reading is within specifications, proceed to next step.
3. Check continuity between ground and Brown terminal. Check continuity between ground and Blue terminal. If continuity exists, replace sensor. If no continuity exists, proceed to next step.
4. Reconnect sensor connector. Attach system checker harness to right side wire harness only, not to ECU. Using an ohmmeter, check resistance between connector terminal No. C3 and C4. Resistance should be 500-1000 ohms.
5. If resistance not within specifications, repair open in Brown and/or Blue wire. If resistance is within specifications, connect a known good ECU and recheck. Replace ECU if original is defective.

CODE - 9 CRK/CYL SENSOR

1. Turn ignition off. Disconnect hazard fuse at battery positive terminal for 10 seconds to reset ECU. Start engine and check for PGM-FI warning light on or off. If light is off, test drive and check again.
2. If light is on, turn engine off. Disconnect sensor connector nearest the sensor. Measure resistance between sensor connector and sensor, Red terminal and White terminal, with an ohmmeter. If ohm reading is not 650-850 ohms, replace sensor. If ohm reading is within specifications, proceed to next step.
3. Check continuity between ground and Red terminal. Check continuity between ground and White terminal. If continuity exists, 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. Using an ohmmeter, check resistance between connector terminal No. C1 and C2. Resistance should be 650-850 ohms.
5. If resistance not within specifications, repair open in Red and/or White wire. If resistance is within specifications, connect a known good ECU and recheck. Replace ECU if original is defective.

Code 10, TA Sensor Test Chart, Integra (1 of 2). Scheme 28

Code 10, TA Sensor Test Chart, Integra (2 of 2). Scheme 29

Code 13, PA Sensor Test Chart, Integra (1 of 2). Scheme 30

Code 13, PA Sensor Test Chart, Integra (2 of 2). Scheme 31

CODE 14 - ELECTRONIC IDLE CONTROL VALVE (EICV)

1. Turn ignition off. Remove hazard fuse at battery positive terminal for 10 seconds to reset ECU.
2. Start engine and check PGM-FI warning light is on or off. If light is off, test drive and recheck. If light is on, stop engine. Disconnect EICV connector. Using an ohmmeter, check resistance between the 2 connector terminals.
3. Resistance should be 6-20 ohms. If not within specifications, replace EICV. If resistance is within specifications, proceed to next step.
4. Check for continuity to ground on each 2 EICV connector terminals. If continuity exists, replace EICV. If no continuity exists, turn ignition on. Connect a voltmeter between Black/Yellow (+) terminal and White (-) terminal.
5. Check for battery voltage. If no battery voltage exists, proceed to step 6). If battery voltage exists, disconnect 17P connector from ECU and check for battery voltage again. If battery voltage now exists, repair short in wire between ECU connector terminal No. A11 and EICV. If battery voltage still does not exist, proceed to step 10).
6. If no battery voltage exists, measure voltage between (+) terminal in step 4) and body ground. If battery voltage now exists, proceed to step 7). If battery voltage still does not exist, Check No. 4 fuse and repair open Black/Yellow wire between fuse and EICV.
7. If battery voltage exists, turn ignition off. Reconnect EICV connector to EICV. Connect system checker harness "A" connector to main wire harness only, not ECU.
8. Turn ignition on. Using a voltmeter, measure voltage between connector terminal No. A11 and No. A18. If battery voltage exists, proceed to step 9).
9. Connect a known good ECU to vehicle and recheck. If fault no longer exists, replace original ECU.

Integra Wiring Diagram. Scheme 32