| 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 in GENERAL INFORMATION. |
Circuit Description
While ignition switch is off, battery positive voltage is supplied to terminal BATT of ECM for DTCs memory and air-fuel ratio adaptive control value memory, etc. If DTC is set, there is an open in back up power source circuit or a faulty ECM.
Diagnostic Aids
- If DTC P0560 is set, ECM does not store another DTC.
- Read freeze frame data using hand-held tester or OBD-II scan tool, as freeze frame data records engine conditions when a malfunction is detected. When troubleshooting, it is useful to determine whether vehicle was running or stopped, engine was warmed up or not, air-fuel ratio was lean or rich, etc. at time of malfunction.