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Fuel Injection and Ignition Diagnostic Procedures in LH-Jetronic and EZK 116/REX 1.
The fuel injection and ignition systems incorporate a built-in diagnostic subsystem that is able to test various sensors and fuel injection or ignition components and report the results.  This diagnostic system is located behind the driver's side strut tower in the engine compartment with a readout box with several functional modes.  If fault codes related to the emission system are registered, the "Check Engine" lamp on the instrument panel is lit.

To operate the diagnostic system, open the box cover and place the test cable mounted on the side of the box into either socket 2 for LH 2.4 fuel injection diagnostics and component or sensor tests or socket 6 for EZK 116 ignition or California EGR diagnostics.  To operate the system:

1. Diagnostic Test Mode 1: Fault Code Retrieval
• Place the cable into socket 2 (LH2.4 fuel injection test) or 6 (EZK116 or REX1 ignition test) as above
• 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.)
• Refer to Table 1 for the interpretation of fault codes from the LH2.4 Fuel injection System and Table 2 for codes from the EZK 116 Ignition System.
• Move the cable into socket 6 (for ignition codes from EZK116 or REX1) or socket 2 (for fuel injection codes from LH2.4) and repeat the above.

2. Erasing Fault Codes.  After you have retrieved all the Fault Codes in step 1 above, you should erase the system memory.
• Repeat step 1 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 step 1 above with the other cable position mode (2 or 6) to erase FI or ignition codes.

3. Diagnostic Test Mode 2 System Sensor Signal Test as to 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 tran 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.

4. 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.

5.  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.

Table 1: LH2.4 Fuel Injection Fault Codes (* denotes Check Engine lamp goes on)
 

Fault Codes	Fault Condition	Causes of Fault	Symptoms
1-1-1	No faults	N/a	N/a
1-1-2	Fault in FI control unit	FI module fault	None
1-1-3*	Fuel trim (lambda control) too lean or rich	Mixture incorrect; O2S wiring fault	High fuel consumption
1-2-1*	Faulty signal to/from Air Mass Meter	Wiring fault to or in AMM	Various driving problems; fuel consumption
1-2-3*	Signal missing to/from coolant temp. sensor	Wiring fault to or in ECT sensor	Difficult to start engine when cold
1-3-1	Ignition system RPM signal missing on starting	Wiring fault or RPM sensor bad	Engine will not start
1-3-2	Battery voltage too low/high	Poor battery or charging system	No faults evident
1-3-3	Throttle switch idle setting faulty or grounding fault	TPS failure or maladjusted	Above-normal idle speed
2-1-2*	Signal missing/faulty from oxygen sensor	Wiring fault to heated O2S sensor	High fuel consumption, driving problems
2-1-3	Throttle switch full load setting faulty or grounding short	Wiring fault to TPS or TPS failure	No faults evident
2-2-1*	Fuel trim (lambda control) too lean at part load	Lean; air leak; low fuel pressure; bad AMM	Engine stops when starting from cold; high fuel use
2-2-3	Signal missing to/from idle air control valve	Circuit fault to IAC or faulty IAC valve	Engine difficult to start; low idle speed
2-3-1*	Fuel trim (lambda control) too lean or too rich at part load	}If too lean: air leaks, low fuel pressure, bad sensor	}Engine stops when starting from cold; high fuel use or
2-3-2*	Fuel trim (lambda control) too lean or too rich at idle	}If too rich: high fuel press., leaking injector	} various driving problems
3-1-1	Signal missing from speedometer	Speedo wiring or instrument cluster wiring faulty	Idling problems
3-1-2	Signal missing for knock-related fuel enrichment	Wiring break between EZK terminal 4 and FI #28	No faults evident
3-2-2	Air Mass Meter wire burn-off signal absent or faulty	Wiring break between FI terminal 8 and AMM #4	Various driving problems due to dirty AMM wire

 

Table 2: EZK 116 Ignition Fault Codes (* denotes Check Engine lamp goes on)
  (REX 1 ignition system codes are shown in italic)
 
 

Fault Codes	Fault Condition	Causes of Fault	Symptoms
1-1-1	No fault detected	N/a	N/a
1-4-2*	Control module fault	EZK ignition control module faulty	Engine runs in limp-home mode
1-4-3*	Knock sensor signal absent or faulty	Faulty wiring to/from/in the knock sensor	Poor acceleration, low power, high fuel cons.
1-4-4*	No load signal from fuel injection system	Faulty wiring from LH to EZK; bad LH module	Engine lacks power; stalls; doesn't start or is jerky
1-5-4*	EGR system flow too high	Faulty EGR valve or controller, wiring; engine thermostat	Engine idles unevenly
2-1-4	RPM sensor signal absent intermittently	Faulty RPM sensor, wiring or incorrect installation	Engine will not start; runs rough; overheats
2-2-4	Engine coolant temp (ECT) sensor signal absent or faulty	Faulty wiring or ECT sensor	No fault symptoms evident
2-3-4	Throttle Position Switch (TPS) idle signal faulty	Faulty wiring or TPS; TPS adjusted incorrectly	Poor hot starting; poor idling; limp-home operation
2-4-1*	EGR system flow too low	Faulty wiring, EGR, EGR vacuum or controller; EGR temp sensor	Poor idling
4-1-3*	EGR temperature sensor signal faulty or absent	Faulty EGR temp sensor or wiring	No fault symptoms evident
3-3-4	Throttle Position Switch (TPS) in idle position (REX 1 only)	Faulty wiring or TPS; TPS adjusted incorrectly