| WARNING | Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS . |
| CAUTION | If 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. |
Circuit Description
Constant battery voltage is supplied to +BM terminal of ECM as the power source for the Electronic Throttle Control System (ETCS). DTC is set when battery voltage does not exist at +BM terminal of ECM. If DTC P1127 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. Possible causes are
- Defective fuse.
- Power source for ETCS circuit is open or shorted.
- Defective ECM.
Diagnostic Aids
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.
Scheme 325
- Remove THRO fuse (15-amp) from fuse/relay box at driver's side front corner of engine compartment. (Scheme 325) Check THRO fuse. If THRO fuse is okay, reinstall THRO fuse and go to next step. If THRO fuse is defective, replace fuse and check for short in Gray wire between THRO fuse and ECM. See WIRING DIAGRAMS article. ECM is located behind glove box. see scheme 3 Repair wiring as necessary.
- Remove glove box for access to ECM with electrical connectors still installed on ECM. see scheme 3 Using voltmeter, check voltage between body ground and terminal No. 6 (Gray wire) at ECM electrical connector E7. see scheme 7 This is the +BM terminal on ECM. Voltage should 9-14 volts. If voltage is within specification, replace ECM. If voltage is not within specification, repair open or short in wiring harness and electrical connectors between battery, THRO fuse and +BM terminal on ECM. See WIRING DIAGRAMS article.