Hardware        




The Check Engine Light Explained

Note that the Check Engine Light (CEL) is also referred to as the Malfunction Indication lamp (MIL) in some documentation.

If the CEL) remains on during normal operation then the ECU has detected a possible fault. The fault codes can be read from the ECU using the Check Engine Light. Some models have an empty slot in the fuse box that requires a fuse to be inserted but most models have either a 4-pin or a 6-pin connector that requires a wire link to be inserted to place the ECU into test mode.

The following table lists many of the CEL fault codes, note that there are other fault codes that can only be accessed using a scan tool, those codes do not light the CEL.
Typical Connector locations:
First gen. Vitara/Sidekick/Tracker
Underneath the bonnet either beside the battery or beside the (UK) drivers side headlamp.
Jimny
Behind glovebox
Baleno
Under bonnet, inside relay box
GV/Grand Vitara
Under bonnet beside ignition coil (if fitted)


Six pin connector:




There are two input 'switches', the Diagnostic Switch Terminal (DST) and the Test Switch Terminal (TST) and two output lines the Diagnostic Output Terminal and the Duty Output terminal. The Diagnostic Output Terminal is simply a connection to the Check Engine Light (CEL). Diagnostic modes are selected by placing jumpers between the switch terminals and the ground terminal.
The test modes are given in the table below. '0' represents a grounded input, '1' represents a non-grounded input.


Input Terminals
Output
DST (B)
TST (E)
1
1
No Diagnostic Outputs*
1
0
Ignition Timing to Initial Settings
0
1
Diagnostic Codes Output on Diagnostic Output Terminal*, ISC Duty Cycle on Duty Check Terminal
0
0
Diagnostic Codes Output on Diagnostic Output terminal*, Injector Duty Cycle on Duty Check Terminal


* When CEL is ON this terminal will be 'High', when CEL is OFF this terminal will be 0V.

This is better illustarted by the image below which shows a jumper inserted in the diagnostic socket of a Suzuki Baleno:



Four pin connector:


The four pin connector is similar to the six pin connector. The Diagnostic switch terminal outputs the fault codes on the The Test Switch Terminal sets the ignition timing to base settings.


The test modes are shown in the table below. '0' represents a grounded input, '1' represents a non-grounded input.


Input Terminals
Output
DST (B)
TST (D)
1
1
No Diagnostic Outputs
1
0
Ignition Timing to Initial Settings
0
1
Diagnostic Codes Output on CEL, ISC ouput on Duty Check Terminal
0
0
Diagnostic Codes Output on CEL, Injector Duty Cycle output on Duty Check Terminal


Fault Codes:

Fault codes are indicated by flashing the CEL as shown in the picture below. In this case the fault code '21' is being output. The light is switched ON twice in quick succession to indicate a 2. The light is then OFF for 1 sec and then flashed once to indicate a 1. There is then a 3 sec period with the light off before the next code is indicated. If there are no other codes then the sequence repeats.


The YouTube video below shows a Code 23 (ATS Signal High) being flashed on a Suzuki Baleno Check Engine Light. You will need to have ActiveX enabled to view this video.





Below is a description of the codes and some hints on fault diagnosis. In all cases there is a possibility that the ECU is damaged, however this is unlikely unless the CEL does not light, remains on permanently even with a jumper in the connector, or you have the main and fuel pump relays clicking continuously.
Diagnostic Code
Diagnostic Item
Possible Fault
12
Normal
No fault or fault in not monitored circuit
13
O2 Sensor
ECU will drive mixture rich or lean.
If O2 reading doesn't change or is slow to change a fault is flagged
13
Barometric Sensor
Barometric sensor reading High or Low (Diesel)
14
Water Temperature Sensor
WTS signal High
Open circuit sensor or bad ground
14
Needle Movement Sensor
Needle Movement Sensor High or Low (Diesdel)
15
Water Temperature Sensor
WTS signal Low
Short circuit in sensor or wiring shorted to ground
21
Throttle Position Sensor
TPS signal High
TPS faulty or open circuit signal or ground connection
22
Throttle Position Sensor
TPS signal Low
TPS faulty, short circuit signal or open circuit power connection
23
Air Temperature Sensor
ATS signal High
ATS open circuit or bad ground
24
Vehicle Speed Sensor
VSS faulty, Broken Speedo cable
25
Air Temperature Sensor
ATS signal Low
ATS short circuit, signal wire short circuit or open circuit power connection
26
O2 Sensor (Right bank)
V6 engines only
If O2 reading doesn't change or is slow to change a fault is flagged
27
Compensation Resistance Signal
(Diesel only?)
Open circuit or shorted
28
Glow Plug Relay Signal
(Diesel only)
Open circuit or shorted
31
Manifold Pressure Sensor
MPS signal Low
MPS faulty, open circuit power connection
31
Boost Sensor Signal
(Turbo)
Boost sensor Signal Low
Boost sensor faulty, open circuit power connection
32
Manifold Pressure Sensor
MPS signal Low
MPS faulty, open circuit power connection
32
Boost Sensor Signal
(Turbo)
Boost sensor Signal High
Boost sensor faulty, open circuit ground connection
33
Volume Airflow Sensor
Volume Airflow Sensor too High or too Low
Airflow sensor faulty or faulty wiring
33
Mass Airflow Sensor
MAF Signal High
MAF faulty or bad ground connection
34
Mass Airflow Sensor
MAF Signal Low
MAF faulty or bad power or signal connection
35
NE Sensor
(Diesel only)
 
37
ABS
ABS malfunction - does not set MIL!
41
Ignition Fail Safe Signal
Bad connection to noise suppressor, bad noise suppressor
41
Timer Control Valve Signal
(Diesel only)
 
42
Crank Angle Sensor
CAS signal not present during cranking, only shows while cranking!
Faulty CAS or bad connection
43
Knock Sensor circuit malfunction
Faulty Knock Sensor or bad connection
43
Starter Signal
(Diesel only?)
Starter signal on during engine running
Starter signal off during cranking
44
Idle switch
Idle Switch Open
Faulty Idle switch, badly adjusted TPS, open circuit signal or ground connection
45
Idle Switch
Idle Switch Closed
Faulty Idle Switch, badly adjusted TPS or signal shorted to ground
46
IAC Valve
 
47
CMP Sensor
camshaft Position Sensor
51
Exhaust Gas Recirc Valve
EGR modulator faulty, exhaust passageway clogged, bad VSV, vacuum leak, catalytic converter fault
52
Fuelling Fault
Bad injector, dirty injector, excessive fuel pressure
52
Spill Valve Signal
(Diesel)
Stuck spill valve, open or shorted wiring
53
Ground Circuit Error
California ECU in non-Calif vehicle. Non-Calif ECU in Calif. vehicle
54
5th Gear Switch
 
61
Shift Solenoid Valve A (#1)
(A/T)
 
62
Shift Solenoid Valve A (#1)
(A/T)
 
63
Shift Solenoid Valve B (#2)
(A/T)
 
64
Shift Solenoid Valve B (#2)
(A/T)
 
65
TCC Solenoid Valve Electrical
(A/T)
 
66
TCC Solenoid Valve Electrical
(A/T)
 
71
Test Switch
Test Switch Terminal Grounded (Samurai only?)
Wire link still in diagnostic plug or signal shorted to ground
71
Memory Error
(Late models)
ECU internal write error or checksum error
72
Transmission Range Switch circuit malfunction
(A/T)
 
73
Fuel Temperature Sensor
(Diesel)
Fuel temp. sensor, open or shorted wiring
75
Output Speed sensor Circuit Malfunction
(A/T)
 
76
Input/turbine Speed sensor Malfunction
(A/T)
 
ON - Not Flashing
ECU
ECU Failed
Immobiliser
81
Immobiliser/ECU
Immobiliser codes not matched (ECU side)
82
ECU
ECU Internal fault
83
Immobiliser/ECU
Serial Data Link
84
ECU
No Immobiliser codes registered in ECU








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