1999 Toyota Sienna Case Study: Engine Control Module (ECM) Mismatch - MechoMedics

Sunday, 21 January 2018

1999 Toyota Sienna Case Study: Engine Control Module (ECM) Mismatch

Hi Trainers, Automobile Technicians, Mechanics and Diagnosticians (I’ll just shorten it to DiagTechMech), we will discuss about a 1999 Toyota Sienna that had its Electronic Control Module (ECM) stolen and key misplaced. The ‘Rewire’ put on this job tried putting a 2001 ECM (TOYOTA 89661-08061) to start this Multi-Purpose Van (MPV), with repeated starting attempts and resulting failure; he cut the immobilizer 30mm gauge wire (WHT/BLK) {WHT/BLK wire connecting Transponder Key Amplifier to Junction Connector (J/C2 and J/C3) and to Ground}. This means the Transponder Key Amplifier (TKA) was no longer operative. He also cut the wire to the security buzzer and this resulted in the continuous flashing of the Hazard lights, blinking of Digital Time display, continuous blinking of the security light and buzzer beeping. The Vehicle started but with very erratic performance and multiple misfire that made the MPV to stall at Low RPM.

Diagnosis revealed that there was no communication between the Scan Tool and the ECM, Immobilizer, e.t.c. Diagnosis also revealed a different ECM part number for this vehicle, and hence I’ll call this an ECM Mismatch Case. By inputingthe Vehicle Identification Number (VIN)  4T3ZF13C0XU146759 on a TOYOTA DIY page or even on a Google search, you would have a guide on choosing the right ECM, I used this as an alternative as it was an off-station job, 1998-1999 Toyota Sienna Engine Control TOYOTA 89661-08030 or 08040 or 08050. 
I bought the ECM TOYOTA 89661-08030 and this resulted in a Crank: No start condition with DTC B2796 and no Communication in Immobilizer system; this made me reexamine the immobilizer wiring and I was more disturbed with all wires connected and still the car would not start. I had communication with ECM and Immobilizer with my Scan Tool but the major fault of Not Starting was not yet sorted. I ordered for an ECM replacement by the vendor that supplied the first one, and the new ECM TOYOTA 89661-08050 started the Vehicle on the first attempt and communication with Diagnostic Scan Tool was good; all flashing hazard Light and Blinking Security and Digital Clock stopped. Case dismissed.

Replacement of Engine Control Module (ECM) and other Control Modules is a critical process as this  determines if the Engine operation would be as excellent as you had it before or not. Control Modules could have a part functional and another part inoperative, or we could say it would not operate a sensor responsible for Fuel Consumption Control i.e. Air/Fuel Sensor Circuit, Oxygen Sensor Circuit, e.t.c. Hence with replacement of any Vehicle Module, thorough adaptation, calibration, programming and diagnosis on all systems should follow and a Test Drive so as to ensure proper operation and communication.
Secondly some Vehicle models and brands share close similarities but have varying internal designs and operations. But in all this, a VIN is always unique and belongs to a single Vehicle. Hence electronic parts are best selected with the use of their VIN.

The wrong ECM also belonged to a 1MZ-FE Toyota Engine, but just because structures look similar does not mean their Sensors, Actuators and Modules connection and wiring are the same and hence operations would differ.  Stay informed and SAFE!

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