how to do a diagnostic

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Originally Posted by 90MarkIII

This is a great forum/thread! I read through the previous 4 pages and didnt see anything on code 26 on 1990 turbo supra, and this code is not in the manual. Just bought the car a month ago and have been restoring it to stock. Everything has been going well until it started intermittently started cutting of all power under heavy acceleration. It always havens from about 3000you rpm and up. Anyone ever had a problem with this code?

It's covered in the TSRM, look in the EFI section under "Diagnosis System". It's an over-rich condition detected.




Here are the common codes for Toyota vehicles 1986-95 (Valid for 1986 - 1995... I think they were actually using up to 98 or so in some vehicles but that may not be the case with the USDM and other markets)

Code 11 Momentary interruption in power supply to ECU (electronic control unit or computer) up to 1991
Code 12 Engine revolution signal missing
Code 13 Rpm signal to ecu missing above 1000 rpm
Code 14 Igniter signal to ecu missing
Code 16 A/T control signal missing from ecu
Code 21 Main oxygen sensor signal fault
Code 22 Water temperature sensor circuit fault
Code 23 and 24 Intake air temperature signal fault
Code 25 Air/fuel ratio LEAN
Code 26 Air/fuel ratio RICH
Code 27 Sub-oxygen sensor signal or heater circuit fault
Code 28 No.2 oxygen sensor/heater signal fault
Code 31 and 32 Air flow meter circuit or Vacuum sensor signal fault
Code 34 and 36 Turbo-charging pressure signal fault
Code 35 Altitude compensation sensor signal fault
Code 41 Throttle position circuit fault
Code 42 Vehicle speed sensor circuit
Code 43 No starter signal to the ecu
Code 51 AC signal on; DL contact off (in trany shifter with diagnostic connector jumped)
Code 52, 53 and 55 Knock sensor fault
Code 71 EGR system malfunction
Code 72 Fuel cut solenoid signal fault
Code 78 Fuel pump control signal fault
Code 81, 83, 84 and 85 TCM communication fault