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***ECU Diagnostic Codes***


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After my Engine Management light came on I did hours of browsing and research and found this
I thought it may be of use for some 1 else as I couldn't find this on UKSO site
Hope it helps
ECU Diagnostic Codes for many Toyota ECUs


Some codes may not exist in earlier or non-applicable engine ECU’s but all codes are common among many Toyota ECUs.

It is essential that you do have the proper manuals and skills necessary to perform diagnostic and repairs.

This list is to assist those who are qualified in obtaining some information out of the ECU on cars equipped with factory units.

Diagnosis System: To obtain ECU codes, proceed as follows:

Initial conditions must be met for codes to appear in normal output.

• Battery Voltage must be 11V or more
• Throttle valves must be fully closed (on newer engines)
• Accessories switched off
• Engine at operating temperature

1. Turn the ignition switch ON. (Do not start engine)

2. Short terminals TE1 and E1 of the check connector of the diagnosis connector cluster.

Diagnostic Codes:

Normal Operation: (no malfunction)

The light will alternatively blink ON and OFF at 0.26 second intervals.

Malfunction Codes Indication

In the event of a registered malfunction, the light will blink every 0.52 second. The first series of blinks will equal the 1st digit of a 2 digit code and after a 1.5 second pause; the second series of blinks will indicate the 2nd digit.

If there are 2 or more codes, there will be a 2.5 seconds pause between each signalled code.

After all codes have flashed, there will be a 4.5 second interval and the codes will repeat until TE1 and E1 has been disconnected.

2-Trip detection logic:

Diagnostic Codes 20-29 are usually indicated with 2 -trip logic. This means that the ECU will need two repeated engine operational cycles, with the same problem for the code to be indicated, minimizing the false codes. The ignition must be switched OFF between the 2 successive engine operations.

Test Mode: (1989 and later ECU, with variation in models)

In this mode, the ECU will have increased sensing ability for malfunction detection. It can also detect starter signal circuit, and air conditioning components. The same codes also will be detected as those of the normal modes.

In the same manner and conditions as the normal diagnostic:
1. Short the TE2 and E1 of the diagnostic connector.
2. Turn ignition ON to begin diagnosis in TEST mode.
3. To check that the TEST mode is operational, confirm that the warning light flashes with ignition in ON position.
4. Start the engine and drive the vehicle at or faster than 10km/h (6mph). If the speed fails to reach this the ECU will falsely report that the starter and speed sensor is malfunctioning. (Code 41 and 42)
5. After test drive, short connectors TE1 and E1
6. Read diagnostic codes.

Be sure to Remove SST from check connector when finished.

*Warning:* Test mode will not start if terminals are shorted after ignition is turned ON. Code 51 (AC compressor switch signal) is erratic by nature and will sometimes come on without malfunction.



Code | Signal Diagnosis and Common Trouble Area

1 System OK

2 MAP Sensor or Circuit

3 Ignition Signal from Amplifier

4 CTS/Circuit

6 RPM Signal or Circuit

7 Throttle Position Sensor (TPS) or Circuit

8 ATS/Circuit

9 Vehicle Speed Sensor/Circuit

10 Cranking Signal or Circuit

11 A/C Switch or Circuit

12 RPM Signal
No G or NE signal present for 2 seconds during cranking
Open G circuit
Open, short in G or NE circuit.
Distributor
ECU

13 RPM signal
No NE signal for 50msec at 1000rpm.
Open G circuit
Open, short in G or NE circuit.
Distributor
ECU

14 Ignition No IGF signal to ECU for 4 consecutive IGT signal during engine running
Open/short in IGF/IGT signal from Igniter to ECU
Igniter malfunction
ECU

15 Starter Signal Circuit
Coil pack wires

16 ECT Control Signal or Circuit

21 O2 sensor Open/short in heater circuit of Oxygen (O2) sensor for 0.5 seconds
Amplitude of O2 sensor reduced to 0.35-0.70V continuously for more than 60 seconds
O2 sensor
Vacuum sensor
ECU


22 Water Temperature Sensor no signal at THW
Water temperature sensor
ECU

24 Intake Air Temp sensor no signal at THA
Intake air temp sensor
ECU

25 Air/Fuel mixture Lean Oxygen (O2) sensor output in less than 0.45 volts for at least 90 seconds when O2 sensor is warmed and 1500 rpm or above.
Open injector circuit
Lack of fuel pressure
Ignition system
Vacuum sensor
O2 sensor
ECU

26 Oxygen (O2) Sensor Rich Signal or Circuit

27 Oxygen (O2) Sensor/Circuit

28 Oxygen (O2) Sensor/Circuit

31 Vacuum Sensor
No signal at Vacuum sensor (PIM)
Vacuum sensor to ECU

32 Vane Airflow Sensor or Circuit

33 ISCV (Idle speed control valve)
Open or short in ISCV circuit
ISCV Valve

34 Turbo Pressure Signal or Circuit

35 Turbo Pressure Signal or Circuit

41 Throttle Position Sensor (TPS)
No signal for 0.5 seconds or more at ignition ON. (VTA)
ECU

42 Vehicle Speed Sensor (VSS)
No speed sensor signal to ECU when loaded driving condition with engine speeds 2000 to 5000 rpm.
For 8 seconds or more.
ECU

43 Starter No starter signal to ECU when cranking in TEST mode.
Terminal STA on ECU
Starter signal circuit
Starter relay
Ignition switch

47 Throttle Position Sensor (TPS) or Circuit

51 Switch Condition Signal displayed when A/C is on when TE1 and E1 connected in test mode
A/C switch
Accelerator pedal, cable
ECU

52 #1 Knock Sensor
No KNK1 signal to ECU
Knock sensor loose
Malfunctioning knock sensor

53 #2 Knock Sensor
No KNK2 signal to ECU
Knock sensor loose
Malfunctioning Knock Sensor

54 Turbo Intercooler Signal or Circuit

55 Knock Sensor or Circuit

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how do we get the mods to make it sticky like I say I was looking around for hours to find something that was user friendly as most I found was very confusing this did the job in minutes


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  • 1 year later...

Hi guys, check engine light came on throwing codes 12 and 42 > rpm and speed faults> problem is the car runs fine tachometer and speedo work ok, reset the ecu by unplugging 15a fuse, codes clear but reappear after a day, I'm running a blitz access ecu, I hope the ecu isn't playing up, is there any other checks I could do or replace igniter or dizzy before condemning the ecu?

Thanks

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