ECU Diagnostics
Description:
Most EFI Suzukis (maybe all?) have two diagnostic interfaces for the ECU. One diagnostic connector allows codes to be read by counting the flashes from the Check Engine Light after jumping two
of the pins with a wire link.
The second connector is either a 16-pin OBD2 (J1962) connector or a 12-pin ALDL type connector, this connector is for use with a scan tool. Models equipped with the ALDL connector use a Suzuki proprietary interface known as the Serial Data Link (SDL). Models with an OBD2 connector use SDL, OBD2 (ISO-9141-2) or OBD2 CANBus.
Airbag, ABS and transmission controllers usually have there own test connectors, these are not covered here.
The second connector is either a 16-pin OBD2 (J1962) connector or a 12-pin ALDL type connector, this connector is for use with a scan tool. Models equipped with the ALDL connector use a Suzuki proprietary interface known as the Serial Data Link (SDL). Models with an OBD2 connector use SDL, OBD2 (ISO-9141-2) or OBD2 CANBus.
Airbag, ABS and transmission controllers usually have there own test connectors, these are not covered here.
Check Engine Light Method
Some early models have an empty slot in the fuse box that requires a fuse to be inserted. Most models have either a 4-pin
or a 6-pin connector that requires a wire link to be inserted to pull the fault codes.
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Typical Connector locations:
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First gen. Vitara/Sidekick/Tracker
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Underneath the bonnet either beside the battery or beside the (UK) drivers side headlamp.
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Jimny
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Behind glovebox
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GV/Grand Vitara
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Under bonnet beside ignition coil (if fitted)
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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.
The test modes are given in the table below. '0' represents a grounded input, '1' represents a non-grounded input.
Input Terminals | Output |
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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.
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 |
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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.
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 |
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12 | Normal | No fault or fault in not monitored circuit |
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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 |
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14 | Water Temperature Sensor | WTS signal High Open circuit sensor or bad ground |
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15 | Water Temperature Sensor | WTS signal Low Short circuit in sensor or wiring shorted to ground |
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21 | Throttle Position Sensor | TPS signal High TPS faulty or open circuit signal or ground connection |
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22 | Throttle Position Sensor | TPS signal Low TPS faulty, short circuit signal or open circuit power connection |
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23 | Air Temperature Sensor | ATS signal High ATS open circuit or bad ground |
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24 | Vehicle Speed Sensor | VSS faulty, Broken Speedo cable |
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25 | Air Temperature Sensor | ATS signal Low ATS short circuit, signal wire short circuit or open circuit power connection |
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27 | Compensation Resistance Signal (Diesel only?) | Open circuit or shorted |
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28 | Glow Plug Relay Signal (Diesel only) | Open circuit or shorted |
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31 | Manifold Pressure Sensor | MPS signal Low MPS faulty, open circuit power connection |
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31 | Boost Sensor Signal (Turbo) | Boost sensor Signal Low Boost sensor faulty, open circuit power connection |
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32 | Manifold Pressure Sensor | MPS signal Low MPS faulty, open circuit power connection |
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32 | Boost Sensor Signal (Turbo) | Boost sensor Signal High Boost sensor faulty, open circuit ground connection |
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33 | Mass Airflow Sensor | ||
34 | Mass Airflow Sensor | ||
35 | NE Sensor (Diesel only) | ||
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 |
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43 | Knock Sensor circuit malfunction | Faulty Knock Sensor or bad connection |
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43 | Starter Signal (Diesel only?) | Starter signal on during engine running Starter signal off during cranking |
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44 | Idle switch | Idle Switch Open Faulty Idle switch, badly adjusted TPS, open circuit signal or ground connection |
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45 | Idle Switch | Idle Switch Closed Faulty Idle Switch, badly adjusted TPS or signal shorted to ground |
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51 | Exhaust Gas Recirc Valve | EGR modulator faulty, exhaust passageway clogged, bad VSV, vacuum leak, catalytic converter fault |
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52 | Leaking Injector | Bad injector, dirty injector, excessive fuel pressure |
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52 | Spill Valve Signal (Diesel) | Stuck spill valve, open or shorted wiring |
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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 |
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71 | Memory Error (Late models) | ECU internal write error or checksum error |
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72 | Transmission Range Switch circuit malfunction (A/T) | ||
73 | Fuel Temperature Sensor (Diesel) | Fuel temp. sensor, open or shorted wiring |
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75 | Output Speed sensor Circuit Malfunction (A/T) | ||
76 | Input/turbine Speed sensor Malfunction (A/T) | ||
ON - Not Flashing | ECU | ECU Failed |
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Immobiliser |
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81 | Immobiliser/ECU | Immobiliser codes not matched (ECU side) |
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82 | ECU | ECU Internal fault |
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83 | Immobiliser/ECU | Serial Data Link |
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84 | ECU | No Immobiliser codes registered in ECU |
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Serial Data Link Interface
The ALDL connector has the SDL on pin M, Pins ? and ? provide 12V power and ground for a diagnostic scanner.
SDL uses pin 9 on the J1962 connector, ISO 9141-2 (OBD2) uses only the K-Line (pin 7).
SDL uses pin 9 on the J1962 connector, ISO 9141-2 (OBD2) uses only the K-Line (pin 7).
ALDL Connector
OBD2 (J1962) connector
This is a bi-directional one wire interface. Its existance is not widely publicised, it is usually shown in the wiring diagram as a
single box connected to the ECU and labelled SDL. However as described above it is
connected to an underdash connector. Currently there is only one scanner known to be compatible,
the Tech1 scanner which costs several thousands pounds. I am currently working on a cheap alternative.
There are some variations to the protocol, below I have detailed the protocol used by the later 8v models.
An example:
Send To ECU
Header = $13
Message length = $04
Offset = $00 to unknown (will depend on ECU)
Checksum = all bytes sum to zero
ECU returns
Header = $13
Messsage Length = $04
Data = ?
Csum
The offset is defined by a look up table in the ECU. This implies that there may be commonality between ECUs. The list below shows the addresses that I have determined so far for the EE88 EPROM. The first column is the OBD address, the second column is the actual memory address being read. I have made a prototype scanner to create the hardware interface. Parameter definitions will be filled in as work progresses.
00 $0044 = Fault Codes
01 $0046 = Fault Codes
02 $0045 = Stored fault codes??
03 $0047 = Stored fault codes??
04 $0187
05 $004D = RPMH, RPM High Byte (RPMH + RPML = RPM/4
06 $004E = RPML, RPM Low Byte
07 $00D5
08 $0093
09 $00DF = WTS
0A $00E0 = ATS
0B $9803 = ECU variant
0C $0070 = TPS Angle (referenced from idle switch
0D $005B = TPS Position
0E $005A = O2 Sensor Volts*2
0F $00AF = ISC Duty Cycle
10 $00FE = Injector Pulse Width High byte
11 $00FF = Injector Pulse Width Low byte
12 $0066 = Manifold Pressure
13 $0040 = Cylinder filling??
14 $00BA = Ignition Timing (degs)
15 $00D8
16 $00F3 = Short term fuel trim
17 $00EB = Long term fuel trim
18 $00E1
19 $00D9
1A $0058 = Battery Voltage * 0.0737288
1B $0188
1C $0186 = Flags? Bit2 = Fuel Pump?
1D $0095
1E $0079
1F $0002 this is a PORT?
So to read the TPS position send:
$13, $04, $0D, $DC
The ECU will respond with:
$13, $04, Position, Csum
Header | Message Length | Address | Checksum |
An example:
Send To ECU
Header = $13
Message length = $04
Offset = $00 to unknown (will depend on ECU)
Checksum = all bytes sum to zero
ECU returns
Header = $13
Messsage Length = $04
Data = ?
Csum
The offset is defined by a look up table in the ECU. This implies that there may be commonality between ECUs. The list below shows the addresses that I have determined so far for the EE88 EPROM. The first column is the OBD address, the second column is the actual memory address being read. I have made a prototype scanner to create the hardware interface. Parameter definitions will be filled in as work progresses.
00 $0044 = Fault Codes
01 $0046 = Fault Codes
02 $0045 = Stored fault codes??
03 $0047 = Stored fault codes??
04 $0187
05 $004D = RPMH, RPM High Byte (RPMH + RPML = RPM/4
06 $004E = RPML, RPM Low Byte
07 $00D5
08 $0093
09 $00DF = WTS
0A $00E0 = ATS
0B $9803 = ECU variant
0C $0070 = TPS Angle (referenced from idle switch
0D $005B = TPS Position
0E $005A = O2 Sensor Volts*2
0F $00AF = ISC Duty Cycle
10 $00FE = Injector Pulse Width High byte
11 $00FF = Injector Pulse Width Low byte
12 $0066 = Manifold Pressure
13 $0040 = Cylinder filling??
14 $00BA = Ignition Timing (degs)
15 $00D8
16 $00F3 = Short term fuel trim
17 $00EB = Long term fuel trim
18 $00E1
19 $00D9
1A $0058 = Battery Voltage * 0.0737288
1B $0188
1C $0186 = Flags? Bit2 = Fuel Pump?
1D $0095
1E $0079
1F $0002 this is a PORT?
So to read the TPS position send:
$13, $04, $0D, $DC
The ECU will respond with:
$13, $04, Position, Csum
OBD2
OBD2 diagnostic links will be either ISO 9141-2 up to around 2006 and CANBus on 2006-on models. These protocols are covered
fairly comprehensively on other sites so I won't detail them here. Diagnostic scanners are available quite cheap and these will access
all standard OBD2 defined data. Below I have listed the manufacturer specific codes defined by Suzuki.
Insert table here.
Insert table here.
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