EGR System Honda Civic III

DESCRIPTION

Honda uses exhaust gas recirculation (EGR) on all models to reduce oxides of nitrogen (NOx) emissions. The system includes a special intake manifold and cylinder head, EGR valve, EGR control valves, EGR switch and EGR control solenoid valves. Vehicles also use a control unit, speed sensor, thermosensor, control switch solenoid valve and vacuum switch.

OPERATION

The EGR system operates only when the engine is at normal operating temperature and only while accelerating or cruising. The vacuum control signal is carburetor ported vacuum. A thermosensor eliminates EGR when engine coolant is below normal operating temperature.

When vehicle is decelerating, manifold vacuum rises and turns on EGR control switch. The EGR control solenoid valve closes and cuts off EGR flow. Vacuum is provided to EGR control switch only above 15 MPH, when the speed sensor opens the throttle opener solenoid valve.

EGR control valves A and B use a ported vacuum signal to control a manifold vacuum flow large enough to operate the EGR valve. With this system, the EGR valve is operated by a signal proportional to airflow through carburetor venturi, ensuring correct EGR flow.

EGR control valves A and B receive vacuum from solenoid B.

EGR VALVE

1. Start engine. Disconnect vacuum hose from EGR valve. Connect a vacuum pump to EGR valve.
2. Apply 6 in. Hg to EGR valve. Ensure vacuum holds steady. Engine should die. If vacuum does not hold, replace EGR valve. If engine does not die, check EGR valve and ports for blockage.

THERMOSENSOR

1. Remove wires from thermosensor. Ensure engine is cold. Check for continuity to block below 167°F (75°C).
2. Check for continuity to cylinder head below 131°F (55°C) on 1300 and High Alt. 1500 HF models or 149°F (65°C) on 1500 except HF models. Check for continuity to cylinder head below 113°F (45°C) on Federal 1500 HF models and below 122°F (50°C) on Calif. 1500 HF models.
3. Warm-up engine to normal operating temperature. Check for no continuity to block above 167°F (75°C). Check for no continuity to cylinder head above 131°F (55°C) on 1300 and High Alt. 1500 HF models or above 149°F (65°C) on 1500 except HF models.
4. Check for no continuity to cylinder head above 113°F (45°C) on Federal 1500 HF models and above 122°F (50°C) on Calif. 1500 HF models. Check for no continuity to cylinder head above 131°F (55°C) on 1300 models or 149°F (65°C) on 1500 models.

Switch A

1. On 1300 and 1500 HF models, disconnect No. 4 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Black/Red wire terminal of vacuum switch when less than 2 in. Hg vacuum is applied to switch.
2. On 1500 except HF models, disconnect No. 4 hose on control box No. 2 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Black/Orange (Blue/Black on hatchback/sedan man. trans. models) wire terminal of vacuum switch when less than 1.2 in. Hg vacuum is applied to switch.

Switch B

1. On Federal 1500 HF models, disconnect No. 1 hose on control box No. 2 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Brown wire terminal of vacuum switch when vehicle speed is more than 10 MPH and more than 6 in. Hg vacuum is applied to switch.
2. Disconnect No. 1 hose on control box No. 2 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Brown/White wire terminal of vacuum switch when vehicle speed is more than 10 MPH and less than 6 in. Hg vacuum is applied to switch.
3. On Calif. 1500 HF models, disconnect No. 12 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Brown wire terminal of vacuum switch when vehicle speed is more than 10 MPH and more than 7.9 in. Hg vacuum is applied to switch.
4. On High Alt. 1500 HF models, disconnect No. 12 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Brown wire terminal of vacuum switch when vehicle speed is more than 10 MPH and more than 4 in. Hg vacuum is applied to switch.
5. On 1500 except HF models, disconnect No. 12 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Brown/White wire terminal of vacuum switch when more than 9.8 in. Hg vacuum is applied to switch.

Switch C

On 1500 except HF models only, disconnect No. 15 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Black/Red wire terminal of vacuum switch when less than 6 in. Hg (3 in. Hg on Calif. man. trans. models) vacuum is applied to switch.

Switch F

On Federal 1500 HF models only, disconnect No. 12 hose on control box No. 1 from vacuum hose manifold. Connect vacuum pump to hose. There should be voltage at Red wire terminal of vacuum switch when more than 12 in. Hg vacuum is applied to switch.

1300 Models

Check for voltage at control unit connector (Blue and Black/Yellow wires) with ignition on. If no voltage at Black/Yellow wire, check fuse and wiring. If there is no voltage at Blue wire, check wire between ignition coil and control unit. Check Black wire for continuity between control unit and ground. There should be continuity.

1500 Except HF Models

Check for voltage at control unit connector (Blue and Black/Yellow wires) with ignition on. If no voltage at Black/Yellow wire, check wiring. If there is no voltage at Blue wire, check wire between ignition coil and control unit. Check Brown/Black wire for continuity between control unit and ground. There should be continuity. Check wiring and fuse between control unit connector (Blue/White wire) terminal and ignition switch start terminal.

1500 HF Models

Check for voltage at control unit connector (Blue and Black/Yellow wires) with ignition on. If no voltage at Black/Yellow wire, check wiring. If there is no voltage at Blue wire, check wire between ignition coil and control unit. Check Black wire for continuity between control unit and ground. There should be continuity.

SPEED SENSOR

1. Raise and support front of vehicle. Push the voltmeter probe into Yellow/Black wire terminal at control box No. 1 connector. Connect negative probe to ground. Start engine.
2. Select second gear (man. trans.) or position "2" (auto. trans.) and accelerate slowly, while observing voltmeter. Voltage should be battery voltage below 6 MPH and no voltage above 12 MPH. If so, sensor is okay. If not, install a new sensor and retest.

COLD ENGINE

1. Disconnect vacuum hose No. 16 from EGR valve and connect vacuum gauge to hose. Start engine and raise engine speed to 4500-5000 RPM. Vacuum should not be available to EGR valve.
2. If vacuum is not available to EGR valve, proceed to HOT ENGINE test. If vacuum is available, check for voltage at EGR control solenoid valve A in emission box No. 1 (Blue wire on 1300 and 1500 except HF, and Yellow/White wire on 1500 HF models).
3. There should be voltage at solenoid. If there is voltage, replace EGR solenoid valve A and retest. If there is no voltage, check the following: On all 1500 HF models except High Alt., check control switch and thermosensor B.
4. Check for voltage at control unit connector (Black/Yellow wire) with ignition on. There should be voltage. If no voltage, check fuse and wiring. Check Black wire for continuity between control unit and ground. There should be continuity. On all other models, check thermosensor B, wiring and fuse. Retest after repairs.

HOT ENGINE

1. Disconnect No. 16 vacuum hose from EGR valve and connect vacuum gauge to hose. Back probe voltmeter positive probe into terminal at control box No. 1 connector (Yellow/White on 1300, Brown/Black on 1500 HF and Gray on 1500 except HF models). Connect negative probe to ground.
2. On 1300 and 1500 HF models, jack up front of vehicle. Support with safety stands, block rear wheels, and set hand brake. Start and warm-up engine (cooling fan must come on). On all models, vacuum and voltage should be as shown in EGR SYSTEM TEST table. EGR SYSTEM TEST Engine Condition & No. EGR Valve Vacuum Specified Voltage 1 Idle No No 2 4500 RPM (1) 1-3 in. Hg (2) No 3 Hard Acceleration (3) 2-6 in. Hg (2) Yes (1) No on 1500 model with man. trans. except HF. (2) Yes on 1500 model except HF. (3) Disconnect and plug No. 12 vacuum hose at control box No. 1 (except Federal 1500 HF). On 1300 and 1500 HF models, vehicle must be in 2nd gear and at more than 10 MPH.
3. If vacuum is available for condition 1, check vacuum hose routing. If no problem found, replace EGR control valves A and B.
4. If there is no vacuum available for condition 2 (1500 auto. trans. and 1500 HF) and condition 3 (1500 man. trans. except HF), connect voltmeter to EGR control solenoid A (Blue on 1300 and 1500 except HF models, and Yellow/White on 1500 HF models).
5. There should be no voltage. If there is voltage, check the following: On all 1500 HF models except High Alt., check control switch and thermosensor B. Check for voltage at control unit connector (Yellow/Black wire) with ignition on. There should be voltage. If no voltage, check fuse and wiring.
6. Check Black wire for continuity between control unit and ground. There should be continuity. All other models, check thermosensor B. If okay, replace control switch and retest.
7. If there is no voltage, disconnect vacuum hose No. 15 from EGR control solenoid valve A. Check for vacuum at 4500 RPM at EGR control solenoid valve A. If no vacuum is available, check vacuum hose routing and carburetor port. If vacuum is available, replace EGR control solenoid valve A and retest.
8. If there is no vacuum, check vacuum line routing and carburetor port. Clean and retest. On 1500 man. trans. except HF models, with vacuum available for condition 2, if there is voltage at Gray terminal, replace EGR control solenoid valve A and retest.
9. On 1300 and 1500 HF models, if there is no voltage available for condition 2, but vacuum is greater than 3 in. Hg, replace EGR control solenoid valve B. On 1500 auto. trans. models, if there is voltage available for condition 2, but vacuum is greater than 3 in. Hg, replace EGR control solenoid valve C.
10. On 1300 and 1500 HF models, if voltage is available for condition 1 and 2, or no voltage is available for condition 3, check vacuum switch B and speed sensor. On 1500 except HF models, if voltage is available for condition 1 or 3, or no voltage for condition 2, check for voltage at control unit connector (Blue wire) with ignition on. There should be voltage.
11. If no voltage, check Blue wire between ignition coil and control unit. Check vacuum switch B. Check for voltage at control unit connector (Black/Yellow wire) with ignition on. There should be voltage. If no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
12. On Federal 1500 HF models, check vacuum with the condition in which the primary air cut-off solenoid valves are on. Vacuum should be 1-2 in. Hg, if not, replace EGR control solenoid valve C and retest.
13. To test EGR valve, start engine and let it idle. Disconnect EGR valve upper hose. Connect vacuum pump to EGR valve. Apply 5.9 in. Hg vacuum. If vacuum remains steady and engine dies, EGR valve is working properly. If vacuum does not remain steady and engine does not die, replace EGR valve and retest.
14. If vacuum remains steady but engine does not die, remove EGR valve. Check EGR valve and manifold for blockage. Clean or replace as necessary and retest.