Mazda MX-5 Miata / Grand Touring. Manual — part 95

CIRCUIT OPEN/SHORT INSPECTION

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION [LF] .)

2. Inspect the following wiring harnesses for open or short circuit (continuity check).

Open Circuit



If there is no continuity, there is an open circuit. Repair or replace the wiring harness.



EGR valve terminal A and PCM terminal 2G



EGR valve terminal B and PCM terminal 2L



EGR valve terminal E and PCM terminal 2K



EGR valve terminal F and PCM terminal 2H



EGR valve terminal C and main relay



EGR valve terminal D and main relay

Short Circuit



If there is continuity, there is a short circuit. Repair or replace the wiring harness.



EGR valve terminal A and body ground



EGR valve terminal A and power supply



EGR valve terminal B and body ground



EGR valve terminal B and power supply



EGR valve terminal C and body ground



EGR valve terminal D and body ground



EGR valve terminal E and body ground



EGR valve terminal E and power supply



EGR valve terminal F and body ground



EGR valve terminal F and power supply

2008 Mazda MX-5 Miata Grand Touring

2008 ENGINE PERFORMANCE Emission System - MX-5 Miata

Fig. 29: Identifying EGR Valve & PCM Wiring Harness-Side Connector
Courtesy of MAZDA MOTORS CORP.

POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [LF]

1. Remove the intake manifold. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [LF] .)

2. Remove the PCV valve.

3. Verify that there is no airflow when pressure is applied to port A.



If there is airflow, replace the PCV valve.

4. Verify that there is airflow when vacuum is applied to port A.

2008 Mazda MX-5 Miata Grand Touring

2008 ENGINE PERFORMANCE Emission System - MX-5 Miata



If there is no airflow, replace the PCV valve.

Fig. 30: Identifying PCV Valve
Courtesy of MAZDA MOTORS CORP.

WARM-UP THREE-WAY CATALYTIC CONVERTER (WU-TWC) INSPECTION
[LF]

1. Connect the M-MDS or equivalent and monitor PIDs as following.



Monitor the WU-TWC using O2S11 PID for upstream HO2S and O2S12 PID for downstream
HO2S.

NOTE:



Make sure that no HO2S DTCs have been detected. If detected, this
inspection is not applicable for WU-TWC inspection.

2008 Mazda MX-5 Miata Grand Touring

2008 ENGINE PERFORMANCE Emission System - MX-5 Miata

2. Monitor the appropriate PIDs.

3. Drive the vehicle for 10 min at 65-96 km/h {40-60 mph} to allow the front catalytic converter to reach

operating temperature.

4. Stop the vehicle and leave it in a safe place.

5. Idle the engine.

6. Record PIDs for 1 min .

7. Select the appropriate PIDs and read the graph.

8. Count the number of times (inversions) that the upstream HO2S graph line actually crosses the 0.5 V line.

Fig. 31: Identifying HO2S Graph Line (5 Inversions)
Courtesy of MAZDA MOTORS CORP.

9. Count the number of times (inversions) that the downstream HO2S graph line actually crosses the 0.5 V

line.

10. Using the following equation, calculate the value of ratio.

Equation

RATIO = Upstream HO2S inversion divided by downstream HO2S inversion

NOTE:



Do not count the number of peaks. Refer to Fig. 31 .

2008 Mazda MX-5 Miata Grand Touring

2008 ENGINE PERFORMANCE Emission System - MX-5 Miata