92-95 Sc300/sc400 Obd1 Code Retrieval
 

Lexus Code Retrieval
Accessing Diagnostic Trouble Codes
The check engine warning light will come on when the ignition switch is turned On and the engine is not running. When the engine is started, the check engine warning light should go off. If light remains on, the self-diagnosis system has detected a fault in the system.

Battery voltage must be 11 volts or more. Throttle valve must be fully closed. Transmission must be in Neutral position. All accessories must be turned Off.
On pre-OBD II models, turn ignition to On, then use a jumper wire to connect terminals TE1 and El of the data link connector, located under the left hand side of the instrument panel. Codes are indicated by the number of flashes of the check engine warning light.

Reading Trouble Codes
If the ECU has detected a system malfunction, the check engine light will blink every .5 second. The first number of blinks will equal the first digit of a two digit diagnostic trouble code and after a 1.5 second pause, the second number of blinks will equal the second digit of same diagnostic trouble code. If there are two or more DTC's, there will be a 2.5 second pause between each. After all DTC's have been output there will be a 4.5 second pause and all DTC's will be repeated as long as the terminals TE1 and El of the data link connector are connected. In the event of two or more DTC's, indication will begin from smaller numbered code and continue in order to the larger. After all DTC have been recorded, remove jumper wire.

Clearing Trouble Codes
After service, the diagnostic trouble code or DTC's retained in the ECU memory must be cleared by remove the EFI fuse for approximately 10 seconds or more, depending on ambient temperature (the lower the temperature, the longer the fuse must be left out) with the ignition switch off. DTC clearing can also be done by removing the battery ground cable, other memory systems (clock) will also be cleared. If the diagnostic trouble code is not cleared, it will be retained by the ECU and appear along with a new DTC in future trouble codes. If it is necessary to work on engine components requiring removal of the battery ground cable, confirm no DTC's are stored. After clearing codes, road test the vehicle to check that a normal operation. If the same diagnostic trouble code appears, the trouble has not been corrected.

OBD1 codes:

12
RPM Signal

13
RPM Signal

14
Ignition Signal

15
Ignition Signal

16
Electronically Controlled Transmission Control Signal

17
CMP No. 1

18
CMP No. 2

21
Main O2S & Heater Signal

22
ECT Sensor Signal

24
IAT Sensor Signal

25
Air–Fuel Ratio Lean Malfunction

26
Air–Fuel Ratio Rich Malfunction

27
Sub O2S Signal

28
Main O2S

29
Sub O2S

31 & 32
Air Flow Meter Signal

35
HAC/Barometric Pressure Sensor Signal

41
TP Sensor Signal

42
VSS Signal

43
Starter Signal

47
Sub TP Sensor

48
Secondary Injection System Malfunction

51
Switch Condition Signal

52
KS Signal

53
Knock Control Signal

55
KS Signal

70
EGR System Malfunction

71
EGR System Malfunction

78
Fuel Pump Control




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I'm having a few problems with the diagnosis here,
prob just going to call me a idiot now but, i can seem to locate the 3rd 02 sensor

i am running three codes 21,27,28
21,28 are the mains and 27 is the sub signal where is this sub signal located i ran the entire exhaust form the cat back and i can't find it???

ok so now I'm seeing that some years ago a few people ran into this problem, something with the ECU coolant sensor is bad. i don't have a spare ecu to test this theory.