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DTC P0100: MASS AIRFLOW METER CIRCUIT Toyota Sequoia I

Testing & Diagnostics 1 illustration ~815 words
CAUTIONIf Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, 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 article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.

Circuit Description

Mass Airflow (MAF) meter uses a platinum hot wire which is maintained at a constant temperature by controlling the current flow through the hot wire. Current flow is then measured as an output voltage. MAF meter may also be referred to as airflow meter. DTC is set when ECM detects an open or short in MAF meter circuit for more than 3 seconds. Possible causes are

  1. MAF meter circuit is open or shorted.
  2. Defective MAF meter.
  3. Defective ECM.

Diagnostic Aids

After confirming DTC P0100, use Toyota hand-held tester or scan tool to access CURRENT DATA to confirm MAF meter air flow rate. If MAF meter air flow rate is 0.0 gm/sec., VG circuit may be open or shorted, or power source circuit may be open. If MAF meter air flow rate is 271.0 gm/sec. or more, EVG circuit may be open. Using hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

Scheme 51

Scheme 51: Diagnosis & Repair
Scheme 51: Diagnosis & Repair
  1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Turn ignition on and then turn hand-held tester or scan tool on. Start engine and allow engine to idle. Using hand-held tester or scan tool, monitor MAF meter air flow rate. If MAF meter air flow rate is 0.0 gm/sec., go to next step. If MAF meter air flow rate is 271 gm/sec. or more, go to step 5.
  2. Turn ignition off. Disconnect electrical connector at MAF meter. MAF meter is bolted to top side of air intake hose, near upper cap on air cleaner assembly and contains a Black 5-pin electrical connector. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 3 (Green/Red wire) on MAF meter electrical connector. (Scheme 51) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair open in Green/Red wire between EFI main relay, EFI No. 2 fuse (10-amp) and MAF meter. See «WIRING DIAGRAMS»(ref-133228) article. EFI main relay may also be referred to as EFI relay. EFI main relay and EFI No. 2 fuse are located in fuse/relay box at driver's side front corner of engine compartment.
  3. Turn ignition off. Reinstall electrical connector at MAF meter. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Ensure A/C switch is in OFF position and shift lever is in Park or Neutral. Start engine and allow engine to idle. Using voltmeter, check voltage between body ground and terminal No. 10 (Red/White wire) at ECM electrical connector E7. see scheme 4 This is the VG terminal on ECM. Voltage should be.5-3.0 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
  4. Check for open and short in Red/White wire and electrical connectors between MAF meter and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace MAF meter. See «AIRFLOW METER»(ref-133227-S33806184422002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If wiring harness or electrical connector is defective, repair as necessary.
  5. Turn ignition off. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using ohmmeter, check resistance between body ground and terminal No. 19 (Black/White wire) at ECM electrical connector E7. see scheme 4 The is the EVG terminal on ECM. If resistance is one ohm or less, go to next step. If resistance is greater than one ohm, replace ECM.
  6. Check for open in wiring harness and electrical connectors between MAF meter and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace MAF meter. See «AIRFLOW METER»(ref-133227-S33806184422002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If wiring harness or electrical connector is defective, repair as necessary.

Mass Airflow (MAF) meter uses a platinum hot wire which is maintained at a constant temperature by controlling the current flow through the hot wire. Current flow is then measured as an output voltage. MAF meter may also be referred to as airflow meter. DTC is set when ECM detects MAF meter output is greater than 2.2 volts with throttle valve closed for more than 10 seconds with engine speed of 900 RPM or less, or MAF meter output is less than one volt with Throttle Position (TP) sensor VTA circuit signal voltage of .63 volt or more for more than 6 seconds with engine speed of 1500 RPM or more. Possible cause is defective MAF meter.

This DTC uses two-trip detection logic. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

More articles — Engine Control System Self-Diagnostics