Circuit Test B3

Fig 1: Mass Airflow Sensor (MAF) Circuits

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: air cleaner element, inlet air duct, or throttle body.

1. KOER Code 26: Out of Range. Code 26 indicates MAF sensor voltage is not in range of .20-1.50 DC volts, and a KOEO or Continuous memory code has been set. Service Code 26 first and then the Continuous memory code (56 or 66). For Code 26, go to next step. For Code 56, go to step 10). For Code 66, go to step 4).
2. Voltage Check at VPWR Circuit. Turn key off and disconnect MAF sensor from vehicle harness. Set DVOM on 20-volt scale. Measure voltage between VPWR circuit at the MAF sensor connector and the negative battery post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, go to TEST A2 - VEHICLE BATTERY  , step 1).
3. Checking MAF Sensor Ground. With KOEO and MAF sensor disconnected, set DVOM on 20-volt scale. Measure voltage between VPWR circuit and PWR GND circuit at the MAF sensor connector. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts repair open PWR GND circuit, reconnect MAF and rerun QUICK TEST.
4. Code 66: Continuity of MAF Signal and VPWR Circuits. Code 66 indicates that MAF signal was less than .40 volt during engine operation or KOER SELF-TEST. Possible causes for this fault are: open MAF signal circuit, open VPWR circuit to MAF, open PWR GND circuit to MAF, MAF SIGNAL shorted to ground, Faulty ECA or MAF sensor, air leak before or after MAF sensor, or MAF sensor disconnected. With KOEO and MAF sensor disconnected, disconnect and inspect 60-pin connector. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAF SIGNAL at the MAF sensor connector and test pin No. 50 at the breakout box. Measure resistance between VPWR at the MAF sensor connector and test pins No. 37 and 57 at the breakout box. If both resistances are less than 5 ohms, do to next step. If either resistance is greater than 5 ohms, remove breakout box, repair open circuit, reconnect all components and rerun QUICK TEST.
5. Checking MAF Signal Circuit For Shorts. With key off and MAF sensor disconnected, set DVOM on 200K-ohm scale. Disconnect ECA 60-pin connector, inspect connector and terminals. Install breakout box leaving ECA disconnected. Measure resistance between test pin No. 50 and test pins No. 40, 9 and 60, at the breakout box. If all resistances are greater than 10K ohms, go to next step. If resistance in any circuit is below 10K ohms, repair short circuit and rerun QUICK TEST.
6. Checking Continuity of PWR GND Circuit. With key off disconnect MAF sensor. Set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at MAF sensor connector and battery negative post. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, reconnect MAF sensor and rerun QUICK TEST. If resistance is 5 ohms or less, go to next step.
7. Checking MAF SIG RTN Circuit Continuity. With key off and MAF sensor disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60 pin connector, inspect pins and install breakout box, leave ECA disconnected. Measure resistance between MAF SIG RTN, at sensor connector, and test pin No. 9 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, remove breakout box. Service open circuit an rerun QUICK TEST.
8. Checking MAF Signal for Short to Ground. With key off, breakout box installed, and ECA connected, disconnect MAF sensor. Set DVOM on 20K-ohm scale. Measure resistance between test pin No. 50 and pins No. 9, 40, and 60 at the breakout box. If all resistances are less than 10K ohms, remove breakout box. Replace ECA and rerun QUICK TEST. If resistances are greater than 10K ohms, go to next step.
9. Checking MAF Output. With key off, install breakout box. Ensure ECA and MAF are connected. Set DVOM on 20-volt scale. Measure voltage between test pin No. 50 and the battery negative post. Start engine. If voltage is .20-1.50 volts replace ECA. If voltage is not .20-1.5, replace MAF sensor.
10. Code 56: Rerun SELF-TEST With MAF Disconnected. With key off, disconnect MAF sensor from vehicle harness. Start engine and allow to idle for one minute. Turn key off. Rerun KOEO SELF-TEST. If Code 66 is present, replace MAF sensor and rerun QUICK TEST. If Code 66 is not present, go to next step.
11. Checking MAF Signal for Short to VPWR. With key off, install breakout box and disconnect MAF sensor and ECA. Set DVOM on 200K-ohm scale. Measure resistance between MAF SIGNAL and VPWR at MAF sensor connector. If resistance is greater than 10K ohms, remove breakout box. Reconnect MAF sensor, replace ECA, and rerun QUICK TEST. If resistance is less than 10K ohms, repair circuit short and rerun QUICK TEST.