Circuit Test C
- Install breakout box, leaving ECA connected. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 37 and signal return in SELF-TEST connector. If reading is less than 10.5 volts, go to CIRCUIT TEST B , step 1) for all other engines. If reading is 10.5 volts or higher, go to next step.
- With breakout box installed and ECA connected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 6.0 volts or higher, go to step 4). If reading is 4.0 volts or lower, go to step 5). If reading is between 4.0 and 6.0 volts, go to next step.
- With breakout box installed and ECA disconnected, turn key off. Set DVOM on 200-ohm scale. Measure resistance from test pins No. 26 and 46 to suspect VREF sensor harness connector. If all readings are less than 5 ohms, connect sensors. VREF circuit is okay, repeat QUICK TEST . If any reading is 5 ohms or higher, repair open circuit in VREF or signal return and then repeat QUICK TEST .
- Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 26 and battery ground. If reading is less than 0.5 volts, replace ECA and repeat QUICK TEST . If reading is 0.5 volts or higher, repair short to battery power in EEC-IV harness. Repeat QUICK TEST . Replace ECA if fault still occurs.
- Shorted TPS Sensor. Turn key off and wait for 10 seconds. With breakout box installed and ECA connected, disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 4.0 volts or higher, replace TPS and repeat QUICK TEST . If less than 4.0 volts on models without EGR Valve Position (EVP) sensor, go to step 7). If reading is less than 4.0 volts on models with EVP sensor, go to next step.
- Shorted EVP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect EVP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4.0 volts or higher, replace EVP sensor and repeat QUICK TEST . If reading is less than 4.0 volts, go to next step.
- Shorted MAP/BP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect MAP/BP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4.0 volts or higher, replace MAP/BP sensor and repeat QUICK TEST . If reading is less than 4.0 volts on models without Vane Airflow (VAF) sensor, go to step 9). If reading is less than 4.0 volts on models with VAF sensor, go to next step.
- Shorted VAF Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect VAF sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4.0 volts or higher, replace VAF sensor and repeat QUICK TEST . If reading is less than 4.0 volts, go to next step.
- With breakout box installed and ECA disconnected, turn key off and wait 10 seconds. Disconnect TPS, MAP/BP, EVP, and VAF sensor (if equipped). Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46, and 60. If reading is less than 5 ohms, repair short to ground, connect all sensors and repeat QUICK TEST . If original problem still occurs, replace ECA and repeat QUICK TEST . If reading is 5 ohms or higher, connect sensors, replace ECA and repeat QUICK TEST .