| 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
The Hybrid Vehicle Electronic Control Unit (HV ECU) communicates with the ECM over the HTE + and HTE- circuits. DTC is set when communication between HV ECU and ECM is interrupted for 1.5 seconds or more. Possible causes are
- Defective wiring or electrical connectors.
- Defective HV ECU.
- Defective ECM.
Scheme 331
Scheme 331: Diagnosis & Repair
- Remove glove box for access to ECM with electrical connectors still installed on ECM. see scheme 3 Connect negative lead of oscilloscope to terminal No. 18 (Brown wire) and positive lead to terminal No. 19 (Yellow wire) at ECM electrical connector E9. see scheme 7 This is the HTE - and HTE+ terminals on ECM.
- Turn ignition on and note voltage waveform pattern on oscilloscope. Ensure voltage waveform pattern is as shown in illustration. (Scheme 331) If voltage waveform pattern is not as shown, turn ignition off. Go to next step. If voltage waveform pattern is as shown, turn ignition off. Replace ECM.
- Check for open and short in Brown and Yellow wires and electrical connectors between terminals No. 18 and No. 19 at ECM electrical connector E9 and terminals No. 19 and No. 29 at HV ECU electrical connector H14. This is the HTE - and HTE+ terminals on ECM. For HV ECU electrical terminal identification see scheme 8 HV ECU is located below carpet on floor panel, just below passenger's side of instrument panel. see scheme 4
- If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, replace HV ECU. If HV ECU is replaced, the HV ECU must be reprogrammed for the engine immobilizer system. Engine immobilizer system may also be referred to as Hybrid Vehicle (HV) immobilizer system. For programming procedures, see «HYBRID VEHICLE ELECTRONIC CONTROL UNIT PROGRAMMING»(ref-97394-S29189789812001042700000) under PROGRAMMING.
