1990 - 1992 Toyota Celica All Trac ECU

ECU - Electronic Control Unit Connector.

The 1990–1992 Toyota Celica All-Trac (chassis code ST185) uses an 80-pin waterproof ECU as part of Toyota’s TCCS (Toyota Computer Controlled System), which integrates sequential electronic fuel injection (EFI), electronic spark advance (ESA), and on-board self-diagnosis. The engine is the 3S-GTE, a 2.0-litre DOHC 16-valve turbocharged unit with an intercooler. The ECU connector is a bolt-type waterproof assembly requiring a dedicated engine-control check sub-harness (SST) for terminal voltage measurement; probing bare terminals risks damage to the waterproof seals. Diagnostic fault codes are read by shorting terminals TE1 and E1 on the check connector and counting flashes of the CHECK ENGINE warning lamp.

Connector A

Connector B

Connector D

Notes

• The ECU connector is a waterproof bolt-type assembly. A Toyota special service tool (SST) check sub-harness must be used for live terminal measurement; inserting probes directly into the waterproof connector will damage the seals.
• On-board diagnostics (OBD1): bridge terminals TE1 and E1 on the underbonnet check connector with the ignition on and engine stopped to enter diagnostic mode. Fault codes are output as flashes of the CHECK ENGINE lamp (0.25-second pulses per digit, 1.5-second pause between digits, 2.5-second pause between codes).
• The ECU set bolt on the connector lock must be torqued to the specification given in the repair manual; undertightening can cause intermittent connection faults.
• ECU integrated-circuit terminals are sensitive to electrostatic discharge. Do not open the ECU cover or touch internal components.

Signals

• A20 — ignition timing signal (IGT) from the ignition control module; carries engine RPM information
• A26 — power ground (E1); main ECU earth return
• B3 — intake air temperature sensor (THA); analogue voltage signal proportional to inlet air temperature
• B4 — engine coolant temperature sensor (THW); analogue voltage input used for fuel enrichment and ESA correction
• B6 — primary oxygen sensor (OX); analogue feedback signal used for closed-loop air/fuel ratio control
• B11 — throttle position sensor (VTA); analogue voltage proportional to throttle blade angle
• B13 — manifold absolute pressure sensor; analogue load signal used by the TCCS for fuel and ignition calculations
• D4 — brake light switch input; used by the ECU for idle-up and deceleration fuel-cut logic
• D9 — vehicle speed sensor (SPD); pulse signal proportional to road speed

References

• 1990 Toyota Celica ST185 Repair Manual (RM176U)
• Toyota 3S-GTE Engine Repair Manual RM266E (August 1991)
• 1993 Toyota Celica ST185 Repair Manual (RM305U1)

Category:Car Connectors