Diagnostic Aids

WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.

When DTCs P0171 &/or P0174 exists, the actual air/fuel ratio is too lean. When DTCs P0172 and/or P0175 exists, the actual air/fuel ratio is too rich. If total of short-term fuel trim and long-term fuel trim is within plus or minus 25 percent, the system is functioning normally. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

If DTCs related to MAF, IAT, TPS, HO2S, ECT and/or VPS are output simultaneously, the E2 sensor ground circuit at ECM 34-pin connector E4 terminal No. 2 (Brown wire) may be open. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. For ECM electrical connector terminal identification, see Figure. It may be necessary to check intermediate connectors and ground point in circuit as well. Splice No. 18 is located behind passenger's side of instrument panel, above ECM. Intermediate connector "IE1" is located behind left kick panel. Ground connection "EF" is located on right side of left cylinder head.