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How to Read & Clear Diagnostic Trouble Codes
1990-1994 Lexus LS400

By LexLS.com

Before doing anything read my disclaimer & safety info.

 

Notes

Check engine light on? O/D OFF light blink periodicly? This tutorial will show you how to read the codes for the engine, transmission, airbag, ABS and TRAC systems and how to clear them. Checking for any codes is the first step is diagnosing problems and so everyone should know how to do this. It's simple and will only take you a few minutes. Please do not contact me regarding a specific code you have. The only thing I can tell you is to follow the diagnostic procedure in the repair manual, or you can search on the forums listed on the links page.

If you have a 1990-1994 LS then you have an OBDI system (On-board diagnostics I). This system is what I will cover here.

If you have a 1995 LS on up then you have an OBDII system. Reading codes from these systems requires you to use an OBDII code reader. They typically run around $100. They're not cheap but they can provide many more codes and this makes diagnosis easier. All you need to do is plug the scan tool into the diagnostic port and it displays any codes.

Tools Needed:

1) In order to read the code the battery must be 11v or higher, throttle valve fully closed, transmission in neutral position, and AC turned off. For checking transmission codes the OD switch must in on (pushed in). Connect terminals Te1 and E1 by placing a short piece of wire in the TDCL diagnostic port under the steering wheel. You can also connect these terminals using the check connector located in the engine bay. For engine and transmission codes you place the jumper wire in Te1 and E1. For air bag codes, ABS and TRAC codes, you place the jumper wire in Tc and E1.

2) Turn the ignition switch on. The diagnostic code is read by counting the number of blinks on the appropriate light. For engine codes, you count the blinks on the check engine light. For transmission codes, you count the blinks on the "O/D OFF" light. For airbag codes, you count the blinks on the "airbag" light. For ABS codes, you count the blinks on the "ANTILOCK" light. For TRAC codes, you count the blinks on the "TRAC" light. The codes are all two digits, the first digit is output first, it will pause 1.5 seconds and then output the second digit outputs. Multiple codes can be output. In this case the lowest numbered code is output first followed by a 2.5 second pause between other higher numbered codes in increasing numerical order. Once all stored codes have been output there will be a 4.5 second pause and then the codes repeat. If there are no codes stored then the light will blink continuously, every .25 second. I know this sounds a little confusing but it's very simple once you do it or see an example yourself....

Click here to see a video of engine code 71 (2.5 MB), single code output.

Click here to see a video of transmission codes 63 & 67 (2.9 MB), multiple codes output.

3) Once repairs have been made, clear all stored codes by removing the 20 amp EFI fuse shown above for 10 seconds or more with the ignition switch off. You can also clear codes by removing the negative lead on the battery for the same amount of time, but you'll lose all your clock, radio, and memory settings. After you've cleared the codes go for a road test. If the codes reappear it means you haven't fixed the problem. Note: airbag code 41 cannot be cleared using this method, here's how to clear it. ABS & TRAC codes are cleared by keeping the jumper wire in Tc and E1 and then pressing the brake pedal 8 or more times within 3 seconds.

 

Engine OBDI Diagnostic Codes

The list below will tell you where the problem lies but will not go into diagnosis. Please consult your repair manual for in depth diagnosis, testing and troubleshooting.

12 - RPM signal no. 1

13 - RPM signal no. 2

14 - Ignition no. 1 signal

15 - Ignition no. 2 signal

16 - ECT control signal

17 - No. 1 cam position sensor signal

18 - No. 2 cam position sensor signal

21 - Main oxygen sensor signal (on left bank)

22 - Water temp sensor signal

24 - Intake air temp. sensor signal

25 - Air-fuel ratio lean malfunction

26 - Air-fuel ratio rich malfunction

27 - Sub-oxygen sensor signal (on left bank)

28 - Main oxygen sensor signal (on right bank)

29 - Sub-oxygen sensor signal (on right bank)

31 - Air flow meter signal

35 - HAC sensor signal

41 - Throttle position sensor signal

43 - Starter signal

47 - Sub-throttle position sensor signal

51 - Switch condition signal

52 - No. 1 knock sensor signal

53 - Knock control signal

55 - No. 2 knock sensor signal

71 - EGR system malfunction

 

Transmission OBDI Diagnostic Codes

42 - No. 1 speed sensor signal malfunction

46 - Open or short circuit in no. 4 solenoid valve

61 - No. 2 speed sensor signal malfunction

62 - Open or short circuit in no. 1 solenoid valve

63 - Open or short circuit in no. 2 solenoid valve

64 - Open or short circuit in no. 3 solenoid valve

67 - OD direct clutch speed sensor signal malfunction

68 - Short circuit in kick-down switch

 

Air Bag OBDI Diagnostic Codes

11 - Short in squib circuit or front airbag sensor circuit (to ground)

12 - Short in squib circuit or front airbag sensor circuit (to +B)

13 - Short in squib circuit (between D+ wire harness and D- wire harness)

14 - Open in squib circuit

15 - Open in front airbag sensor sensor circuit

22 - Airbag warning light system

31 - Center airbag sensor assembly malfunction

41 - Malfunction stored in memory

 

ABS OBDI Diagnostic Codes

11 - Open circuit in ABS solenoid relay circuit

12 - Short circuit in ABS solenoid relay circuit

13 - Open circuit in pump motor relay circuit

14 - Short circuit in pump motor relay circuit

21 - Open or short circuit in 3-position solenoid circuit for front right wheel

22 - Open or short circuit in 3-position solenoid circuit for front left wheel

23 - Open or short circuit in 3-position solenoid circuit for rear right wheel

24 - Open or short circuit in 3-position solenoid circuit for rear left wheel

31 - Front right wheel speed sensor signal malfunction

32 - Front left wheel speed sensor signal malfunction

33 - Rear right wheel speed sensor signal malfunction

34 - Rear left wheel speed sensor signal malfunction

35 - Open circuit in front left or rear right speed sensor circuit

36 - Open circuit in front right or rear left speed sensor circuit

37 - Faulty front speed sensor rotor

41 - Low battery voltage or abnormally high battery voltage

43 - Malfunction in TRAC control system

51 - Pump motor is locked, Open in pump motor ground

Always ON - Malfunction in ECU

 

TRAC OBDI Diagnostic Codes

11 - Open in TRAC brake main relay circuit

12 - Short in TRAC brake main relay circuit

13 - Open in TRAC throttle relay circuit

14 - Short in TRAC throttle relay circuit

15 - Electric supply to TRAC motor for a long time (fluid leakage)

16 - Open circuit in pressure switch circuit

17 - Pressure switch remains OFF

19 - TRAC motor ON and OFF operation is higher than a predetermined number of times (accumulator pressure leakage)

21 - Open or short in master cylinder cut solenoid valve circuit

22 - Open or short in accumulator cut solenoid valve circuit

23 - Open or short in reservoir cut solenoid valve circuit

24 - Open or short in sub-throttle actuator circuit

25 - Step motor does not move to a position decided by ECU

26 - Sub-throttle valve does not move even when the sub-throttle valve is controlled to fully open position by ECU

27 - When power supply to step motor is stopped, sub-throttle valve does not reach its fully-open position

44 - During TRAC control, NE signals are not input to the ECU

45 - When idle switch is ON, main throttle position sensor signal is 1.5V or higher

46 - Main throttle position sensor signal is 4.3V or higher, or main throttle position sensor signal is 0.2V or lower when idle switch is OFF

47 - When idle switch is ON, sub-throttle position sensor signal is 1.45V or higher

48 - Sub-throttle position sensor signal is 4.3V or higher, or sub-throttle position sensor signal is 0.2V or lower when idle switch is OFF

49 - Open or short in engine communication circuit

51 - Problem in engine control system

52 - Brake fluid level warning switch ON

54 - Open in TRAC motor relay circuit

55 - Short in TRAC motor relay circuit

56 - TRAC pump motor locked

Always ON - Malfunction in ECU

 

 

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Last revised: Sunday, 16-Mar-2014 18:15:24 CDT