Note. For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.
| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - LEXUS article. |
Circuit Description
MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. DTC P0101 is set when throttle valve is fully closed, MAF sensor output is more than 2.2 volts, and THW is greater than 157°F (70°C).
DTC P0101 will also set when VTA output is .1 volt or more, and MAF sensor output is less than .4 volt for 6 seconds or more at engine speed of zero RPM or more. Possible cause is a faulty MAF sensor.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.