The OBD system:
OBD stands for "On Board Diagnostics".
Many of the LH2.4 cars have a test-socket from which you can read the
fault-codes of the ECU, EZK and TCU. The later model cars (1995-1998 940) has a
serial interface instead of a test socket in which the VST-tool or an OBDII
reader is supposed to plug in to read the fault-codes.
The LH2.4 ECU costantly monitors the following things:
-The control module's own, internal functions.
-Heated oxygen sensor (HO2S) and fuel trim.
-Engine coolant temperature sensor.
-Mass air flow (MAF) sensor.
-Battery voltage.
-Throttle position switch (TP switch).
-Engine speed (RPM) signal from the engine control module (ECM).
-Speedometer signal.
-Knock enrichment signal from the ignition system (does not apply to B 230 F, B
204 FT/GT).
-The idle air control (IAC) valve.
A fault in any of these functions is presented as a diagnostic trouble code
(DTC) in diagnostic test mode (DTM) 1.
The EZK116 constantly monitors the following things:
-The control module's own, internal functions.
-Knock sensor (KS) signal.
-Fuel system load signal.
-Timing pick-up signal.
-Temperature sensor signal.
-Signal from the EGR converter.
-Signal from the EGR temperature sensor.
A fault in any of these functions is presented as a diagnostic trouble code
(DTC) in test function 1.
All the diagnostic trouble codes (DTCs) are reversible. This means that if a
signal has resulted in a diagnostic trouble code (DTC) being stored and it is OK
next time the ignition is turned on, the control module will use the programmed
correct value instead of remaining in “limp-home” mode. But the diagnostic
trouble code (DTC) remains stored in the memory.
Diagnostic Test Mode 1: Fault Code Retrieval.
* Place the cable into socket 2 (LH2.4 fuel injection test) or 6 (EZK116
ignition test).
* Turn the ignition ON to KPII without starting the engine.
* Select Mode 1 by pressing the button once and holding for more than 1 second
but less than 3 seconds.
* The LED lamp will flash in successive series of three digits followed by a
three-second pause. If there are no fault codes stored, it will flash 1-1-1
indicating the fuel injection system is operating correctly.
* Count the successive flashes and record the fault code.
* Press the button again.
* Record the fault code. If it is the same as the previous one, then no
additional codes are stored. Repeat until all the codes stored are retrieved
(maximum of three). If the car is from California you can read up to 17
fault-codes at the same time.
* Refer to the tables below for the interpretation of fault codes from the LH2.4
Fuel injection System and EZK 116 Ignition System.
* Move the cable into socket 6 (for ignition codes from EZK116) or socket 2 (for
fuel injection codes from LH2.4) and repeat the above.
Erasing Fault Codes.
After you have retrieved all the Fault Codes in the steps above, you should
erase the system memory.
* Repeat the steps above and read the fault codes again.
* Press and hold the button for more than five seconds, then release it.
* When the LED lights, press the button again for more than five seconds and
release. If the LED goes off, then the memory is cleared.
* To test that memory is cleared, press the button again for >1 second and <3
seconds. If code 1-1-1 is returned, then the memory is cleared.
* Repeat the steps above with the other cable position mode (2 or 6) to erase
LH2.4 or EZK116 codes.
Diagnostic Test Mode 2: System Sensor Signal Test.
This test is made to know whether signals are received from certain sensors and
switches.
* For vehicles equipped with air conditioning, turn the a/c control to "on."
* Turn the ignition ON to KPII and install the cable into socket 6 for
ignition-related tests.
* Press the button two times for >1 and <3 seconds each. The LED lamp should
flash.
* Check the throttle position switch by turning the throttle pivot wheel
slightly from within the engine compartment. The LED should go out and then
flash code 3-3-4 which indicates proper operation of the TPS. If no code is
flashed and the lamp keeps flashing, the TPS is faulty.
* After the tests, the LED should keep flashing.
* Crank the starter motor. The LED should go out, then flash 1-4-1 for the RPM
sensor. If no code is flashed and the lamp keeps flashing, the RPM sensor is
faulty.
* Install the cable into socket 2 for fuel injection-related tests.
* Press the button two times for >1 and <3 seconds each. The LED lamp should
flash.
Activate the following sensors. If the LED diagnostic code shown (note: this is
not a fault code) is present then the sensor or component is OK:
TPS OK in full load position (when throttle is moved), 3-3-3.
TPS OK in idle position (when throttle is moved), 3-3-2.
RPM sensor signal from ignition OK, 3-3-1.
A/C control on/off OK (when a/c switch is depressed or released), 1-1-4.
A/C compressor start OK, 1-3-4.
Engine idle speed compensation for automatic transmission OK, 1-2-4 (depress the
brake pedal, move the selector to D and then to N).
* Exit Mode 2 by switching off the ignition.
Diagnostic Test Mode 3: Injection System Component Activation Test.
*Turn the ignition ON to KPII and install the cable into socket 2 for
fuel-injection-related tests.
* Press the button three times for one second each time (waiting between >1 and
<3 seconds before pressing again).
* The diagnostic unit then tests selected components: engine coolant fan (if
equipped), fuel injectors, idle air control solenoid valve, carbon filter
solenoid valve (if equipped), cold start valve, radio suppression relay and fuel
pump, each of which you can hear or feel.
* Exit by switching off the ignition.
Alternate Diagnostic Test Mode 3: EGR System Component Activation Test (if
equipped).
* Turn the ignition ON to KPII and install the cable into socket 6 to test the
EGR system controller.
* Press the button three times for one second each time (waiting between >1 and
<3 seconds before pressing again).
* The diagnostic unit then tests the EGR system controller which you can hear or
feel.
* Exit by switching off the ignition.
LH2.4 Fuel Injection Fault Codes (DTC):
Socket position 2.
(The * means that the CEL is lit)
1-1-1 No faults detected.
1-1-2 Fault in control module.
1-1-3* Short-term fuel trim. Faulty control. Fuel trim (lambda control) too lean
or rich.
1-2-1* Mass air flow (MAF) sensor signal. Faulty signal to/from Air Mass Meter.
1-2-3* Engine coolant temperature (ECT) sensor. Signal missing to/from coolant
temp. sensor.
1-3-1 Engine speed signal from ignition system. Signal missing.
1-3-2 Battery voltage. Battery voltage too low/high.
1-3-3 Throttle position (TP) switch at engine idle. Throttle switch idle setting
faulty or grounding fault.
2-1-2* Heated oxygen sensor (HO2S) signal. Faulty or missing signal.
2-1-3 Throttle position (TP) switch at full load. Faulty or missing signal.
2-2-1* Long-term fuel trim, part load. Lean part load.
2-2-3 Idle air control (IAC) valve signal. Faulty or missing signal.
2-3-1* Fuel trim (lambda control) too lean or too rich at part load.
2-3-2* Fuel trim (lambda control) too lean or too rich at idle.
3-1-1 Vehicle speed signal (VSS). Faulty or missing signal. (Also signal from
speedometer).
3-1-2 Knock enrichment signal from ignition system. Faulty signal.
3-2-2 Mass air flow sensor (MAF). Air Mass Meter wire burn-off signal absent or
faulty.
3-4-4 Exhaust gas temperature sensor. Faulty.
EZK 116 Ignition Fault Codes (DTC):
Socket position 6.
(The * means that the CEL is lit)
1-1-1 No faults detected.
1-4-2* Fault in control module.
1-4-3* Knock sensor (KS) signal. Faulty or missing signal.
1-4-4* Load signal. Faulty or missing signal.
1-5-4* EGR. EGR system flow too high.
2-1-4 Engine speed (RPM) sensor. Intermittently absent.
2-2-4 Engine coolant temperature (ECT) sensor. Faulty or missing signal.
2-3-4 Throttle position (TP) switch signal. Faulty or missing signal.
2-4-1* EGR (NTC). EGR system flow too low.
2-4-1* EGR (PTC). EGR system flow too low.
4-1-3* EGR temperature sensor signal (NTC). Faulty or missing signal.
4-1-3* EGR temperature sensor signal (PTC). Faulty or missing signal.
Special Fault Codes (DTC):
ABS Fault Codes (DTC):
Socket position 3.
1–1–1 No fault detected
1–2–5 Faulty signal from at least one wheel sensor
1–3–5 Fault in control module
1–4–2 Brake light switch, open circuit
1–5–1 L/H front wheel sensor, open or short–circ. to supply
1–5–2 R/H front wheel sensor, open or short–circ. to supply
1–5–5 Rear axle sensor, open or short–circ. to supply
2–1–5 Valve relay, open–circuit or short–circuit
2–3–1 L/H front wheel sensor, signal absent
2–3–2 R/H front wheel sensor, signal absent
2–3–5 Rear axle sensor, signal absent
4–1–1 L/H front wheel valve, open or short–circ.
4–1–3 R/H front wheel valve, open or short–circ.
4–1–5 Rear valve open or short–circ.
4–4–3 Pump motor/relay electrical or mechanical fault
TCU Fault Codes (DTC):
Socket position 5.
2-4-2 Turbo control valve. Open-circuit or shorted.
3-1-2 Knocking information. Signal faulty.
3-4-2 A/C blocking relay. Signal faulty.
4-2-1 Pressure sensor. Faulty boost pressure.
4-2-2 Exhaust gas temperature controller. Signal faulty.
4-2-3 Throttle position sensor. Signal faulty.
4-2-4 Load signal. Signal faulty.
4-3-1 Temperature sensor. Signal missing.
ECU:
1: Engine speed signal input 6.5 - cranking, >8 - idle
2: TPS signal input 0.2 - Idle speed, 4 - Full load
3: TPS signal secondary input 1.0 - Idling, 10 - Full load
4: Power supply +30 input 12
5: Signal Ground 0.0 - Separate from power ground
6: Mass air flow 0.0 - Separate from power ground
7: Mass air flow input 2.0 - Idling, 5.0 - Full Load
8: Mass air flow, burn-off Output 4.0 - At burn-off, 0 -otherwise
9: Power supply from main input 12
10: Low-speed pressure sensor, engine cooling fan
11: A/C Time-delay Relay, High-speed pressure sensor, engine cooling fan
12: Diagnostics lead I/O
13: Temp Sensor input 4(-20C) -0.5(80C)
14: A/C, ACC load Signal input 12-Auto, 0-ECON
15: Jumper for cold start 0-no cold start, 12 cold start
16: Diagnostics Lead I/O
17: Chassis Ground
18: Injectors control signal Output 7.1Hz, 2.4-4.5ms
19: EGR Valve Output 12 - inactivated, <12 active
20: Fuel Pump relay signal 1-activ, 12-Ign on
21: Main relay operating circuit Output 1 - Ignition on, 12 - Ignition off
22: Check Engine Light Output 12-off, 1-on
23: EGR Temp Sensor input 4.5 -EGR closed, <4.5 -Open
24: Oxygen Sensor input 0.6 - 1.0 - Rich, 0.0 - 0.4 - Lean
25: Load Signal Tq EZK/DI Output Freq incr with throttle opening
26: Shift-Up light Output 12 - Not activated,0 - Activated
27: EVAP Canister purge valve Output 12 - Open, 1 - Closed
28: PRE-IGNition, DI/APC input 0-Preign, 6.5-stable, 12-knock
* Turbo+ Knock enrichment, trigger
* (B204FT/GT TCU) EGT sensor, trigger
29: Codification input 12 - Automatic transmission
30: Raising engine idle speed input 12-R,D,1,2,3, 0 - P,N, and manual
31: Consumption signal to EDU Output Freq incr with throttle opening
32: Cold start valve Output Battery voltage - Not activated
33: IAC valve Output 5-11 - Idling, no load
34: Speed Sensor input 6 -Rotating, 0 or 12 - Stationary
35: Power Supply +15 input 12-Ign on
EZ116K:
1: OBD diagnostic socket (in some markets: serial interface)
2: Coolant temp sensor
3: Check Engine Light output, shared with ECU pin 22. Signals: 12-off, 1-on
4: PRE-IGNition, output to ECU pin 28. Signals: 0-Preign, 6.5-stable, 12-knock
5: 12v supply, constant
6: 12v supply, switched
7: Throttle idle switch
8: Load Signal Tq, from ECU pin 25
9:
10: Engine speed sensor
11: Engine speed sensor (shield)
12: Knock sensor (shield)
13: Knock sensor
14: EGR, Ground connector on engine (power ground)
15: EGR, converter, control
16: Igntion amplifier drive, trigger
17: Engine speed signal output. Signals: 6.5-cranking, >8-idle
18: Selector wire. Signals: 5v-disabled, grounded-enabled
19: Selector wire. Signals: 5v-disabled, grounded-enabled
20: Ground connector on engine (signal ground)
21:
22: EGR, temperature sensor
23: Engine speed sensor
24:
25:
************************************************************************
TCU (740 and 960 with B204FT/GT):
1: Turbo control valve (boost solenoid)
2:
3: OBD diagnostic socket
4: Relay, engine cooling fan, Control module ECC, ECU Pin 15
5: Relay, engine cooling fan
6: Blocking relay A/C
7: Throttle position (TP) switch/TP sensor
8: Throttle position (TP) switch/TP sensor
9: Temperature sensor TCU
10: Exhaust gas temperature sensor
11: High-speed pressure sensor, engine cooling fan
12: Low-speed pressure sensor, engine cooling fan
13: Combined instrument, speed sensor
14: Load Signal Tq, from ECU pin 25
15: 12v supply, constant
16:
17:
18:
19:
20: Ground connector on engine (signal ground)
21: Ground connector on engine (signal ground)
22:
23: 12v supply, switched
24: Throttle position (TP) switch/TP sensor, ground
25: Temperature sensor TCU, ground
26:
27:
28:
29:
30: PRE-IGNition, DI/APC Pin 4 input 0-Preign, 6.5-stable, 12-knock
31:
32:
33:
34:
35:
Source: http://forums.turbobricks.com