DIAGNOSIS SYSTEM

Entered by Carey Morris from the 1994 Engine Repair Manual

DESCRIPTION

The ECM contains a built-in self-diagnosis system by which troubles with the engine signal network are detected and a malfunction indicator lamp on the instrument panel lights up.

By analyzing various signals as shown in a later table (see table below) the Engine Control Module (ECM) detects system malfunctions relating to the sensors or actuators.

In the normal mode, the self-diagnosis system monitors 19 items, indicated by code No. as shown (see table below).  A malfunction indicator lamp informs the driver that a malfunction has been detected.  The lamp goes off automatically when the malfunction has been repaired.  But the diagnostic trouble code(s) remains stored in the ECM memory (except for code Nos. 16 and 53).  The ECM stores the code(s) until it is cleared by removing the EFI No. 1 fuse with the ignition switch off.

The diagnostic trouble code can be read by the number of blinks of the malfunction indicator lamp when TE1 and E1 terminals on the data link connector 1 or 2 are connected.   When 2 or more codes are indicated, the lowest number (code) will appear first.

In the test mode, 13 items, indicated by code No. as shown (see table below) are monitored.  If a malfunction is detected in any one of the systems indicated by code Nos. 13, 21, 22, 24, 25, 26, 27, 35, 41, 47, 71 and 78 the ECM lights the malfunction indicator lamp to warn the technician that malfunction has been detected.  In this case, TE2 and E1 terminals on the data link connector 2 should be connected as shown later.

In the test mode, even if the malfunction is corrected, the malfunction code is stored in the ECM memory even when the ignition switch is off (except code Nos. 42 and 51).   This also applies in the normal mode.  The diagnostic trouble mode (normal or test) and the output of the malfunction indicator lamp can be selected by connecting the TE1, TE2 and E1 terminals on the data link connector 2, as shown later.

A test mode function has been added to the functions of the self-diagnosis system of the normal mode for the purpose of detecting malfunctions such as poor contact, which are difficult to detect in the normal mode.  This function fills up the self-diagnosis system.  The test mode ca be implemented by the technician following the appropriate procedures of check terminal connection and operation described later.

Diagnosis Inspection (Normal Mode)
MALFUNCTION INDICATOR LAMP CHECK

  • The malfunction indicator lamp will come on when the ignition switch is turned ON and the engine is not running.  HINT: If the malfunction indicator lamp does not lightup, proceed to troubleshooting of the telltale light RH (See page BE-61)
  • When the engine is started, the malfunction indicator lamp should go off.  If the light remains on, the diagnosis system has detected a malfunction or abnormality in the system.

 

DIAGNOSTIC TROUBLE CODE CHECK

  1. Turn ignition switch on.
  2. Connect terminal between TE1 and E1 of data link connector 1 or 2.
  3. Read the diagnostic trouble code from malfunction indicator lamp.  HINT:  If a diagnostic trouble code is not output, check the TE1 terminal circuit.
  4. Check the details of the malfunction using the diagnostic trouble code table (see table below).
  5. After completing the check, disconnect terminals TE1 and E1 and turn off the display.  HINT:  In the event of 2 or more malfunction codes, indication will begin from the smaller numbered code and continue in order to the larger.

 

 

DIAGNOSTIC TROUBLE CODE CHART (2JZ-GTE)

DTC 
No.		 Circuit Diag.. Trouble Code Detecting Condition

Trouble Area

 Normal  Mode Test  Mode Memory
- Normal No code is recorded - - - -
12 G, NE Signal  (No. 1) No "NE" or "G1" and "G2 signal to ECM for 2 sec. or more after cranking.
  • Open or short in crankshaft position sensor, camshaft position sensor No. 1, No. 2 circuit.
  • Crankshaft position sensor
  • Camshaft position sensor No. 1, No. 2
  • Started
  • ECM

ON

 n/a

Yes
13

G, NE Signal  (No. 2)

 No NE signal to ECM for 0.1 sec. or more at 1,000 rpm or more. 
  • Open or short in crankshaft position sensor circuit.
  • Crankshaft position sensor
  • ECM
ON n/a

Yes
NE signal does not pulse 12 times to ECM during the interval between G1 and G2 pulses. 
  • Open or short in crankshaft position sensor circuit.
  • Mechanical system malfunction (skipping teeth of timing belt, belt stretched)
  • Crankshaft position sensor
  • ECM
n/a ON
Deviation in G (G1, G2) and NE signal continues for 3 sec. during idling (throttle fully closed) after engine warmed up.
  • Mechanical system malfunction (skipping teeth of timing belt, belt stretched)
  • Camshaft position sensor No. 1, No. 2
  • ECM
ON n/a
14

Ignition Signal

 No IGF signal to ECM for 4~7 consecutive IGT signals with engine speed less than 3,000 rpm.
  • Open or short in IGF circuit from igniter to ECM
  • Igniter
  • ECM
ON n/a

Yes
16

A/T Control  Signal

 Fault in communications between the engine CPU and A/T CPU in the ECM.

  • ECM

 ON n/a

No
21

Main Heated  Oxygen Sensor  Signal

 Open or short in heater circuit of main heated oxygen sensor (Fr) for 0.5 sec. or more. 
  • Open or short in heater circuit of main heated oxygen sensor.
  • Main heated oxygen sensor heater
  • ECM
ON n/a

Yes
Main heated oxygen sensor signal voltage is reduced to between 0.35V and 0.70V for 60 sec. under condition 

    a) ~ (d). (2 trip detection logic) 

    a). Engine coolant temp.: Between 80° C (176°F) and 95°C (203°F)
    b). Engine speed: 1,500 rpm or more
    c). Load driving (EX. A/T in overdrive (5th for M/T), A/C ON, Flat road, 50 mph <80 km/h>)
    d). Main heated oxygen sensor signal voltage:  Alternating above and below 0.45 V.
  • Main heated oxygen sensor circuit
  • Main heated oxygen sensor
ON ON
22 Engine Coolant Temp. Sensor Circuit Open or short in engine coolant temp. sensor circuit for 0.5 sec or more.
  • Open or short in engine coolant temp. sensor circuit.
  • Engine coolant temp. sensor
  • ECM
ON ON Yes
24 Intake Air Temp. Sensor Signal Open or short in intake air temp. sensor circuit for 0.5 sec. or more.
  • Open or short in intake air temp. sensor circuit.
  • Intake air temp. sensor
ON ON Yes
25 Air-Fuel Ratio Lean Malfunction          
26 Air-Fuel Ratio Rich Malfunction          
27 Sub Heated Oxygen Sensor Signal          
31 Mass Air Flow Meter Circuit          
34 Turbo Pressure Malfunction          
35 Turbo Pressure Sensor Circuit          
35(?) Barometric  Pressure Sensor Circuit          
41 Throttle Position
Sensor Signal		          
42 No. 1 Vehicle Speed Sensor Signal (for A/T)          
No. 1 Vehicle Speed Sensor  Signal (for M/T)
43 Starter Signal          
47 Sub-Throttle Position Sensor Signal          
52 Knock Sensor Signal (front side)          
53 Knock Control Signal Engine control computer (for knock control) malfunction at engine speed between 650 rpm and 5,200 rpm.

ECM

 ON n/a

No
55 Knock Sensor Signal (rear side)          
71 EGR System  Malfunction          
78 Fuel Pump Control Signal          
51 Switch Condition Signal
  1. 3 sec. or more after engine starts, with closed throttle position switch OFF (IDL1).
  2. Park/neutral position switch: OF (Shift position in "R", "D", "2", or "L" position)
  3. A/C switch ON.
  • A/C switch circuit.
  • Throttle position sensor IDL circuit.
  • Park/neutral position switch circuit
  • Accelerator pedal and cable.
  • ECM
n/a OFF

No

 

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