DTC P0100, DTC P0102 OR DTC P0103 — Lexus SC II (2001-2005)

DTC P0100, DTC P0102 OR DTC P0103 Lexus SC II

Code Definitions

DTC P0100: Mass Or Volume Airflow Circuit
DTC P0102: Mass Or Volume Airflow Circuit Low Input
DTC P0103: Mass Or Volume Airflow Circuit High Input

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. (Scheme 45)- (Scheme 46). DTC P0100 is set when ECM detects an open or short circuit for 3 seconds, with engine speed around 4000 RPM. Possible causes are

Open or short in MAF circuit.
Faulty MAF sensor.
Faulty ECM.

Scheme 45

Scheme 46

Diagnostic Aids

After confirming DTC P0100, use scan tool to access CURRENT DATA to confirm mass airflow ratio. If ratio is 0.0 gram/second, VG circuit may be open or shorted or power source circuit may be open. If ratio is 271.0 grams/second or more, EVG circuit may be open. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Scheme 47

Scheme 47: Diagnosis & Repair

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Start engine and allow it to idle. Using scan tool, monitor MAF rate. If scan tool reading is 0.0 gram/second, go to next step. If reading is 271.0 grams/second or more, go to step 3.
Disconnect MAF sensor connector. (Scheme 47) Turn ignition on. Using DVOM, measure voltage between terminal No. 1 and ground. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, locate and repair open wiring between MAF sensor connector and ECM.
Access ECM at left front of engine compartment. Start engine. Ensure transmission is in Park or Neutral and A/C is off. Backprobing connector, measure voltage between terminals E1 and VG at ECM E4 connector. (Scheme 51)- (Scheme 52). If voltage is.5-3.0 volts, go to next step. If voltage is not.5-3.0 volts, check and replace ECM.
Check for an open or short in wiring between ECM and MAF sensor. (Scheme 48)- (Scheme 49). See «ENGINE PERFORMANCE»(ref-158977-S13145987782003110400000) in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring harness as necessary. Also check ECM ground between terminals E1 and EVG of ECM connectors E3 and E4. (Scheme 50) If wiring is okay, replace airflow meter assembly.