YODA OBD1 In Depth

The YODA OBD1 Bluetooth Transmitter connects to the Data Link Connector(DLC) port of Lexus and Toyota vehicles to read ECM data then send it to a smartphone app.

Vehicle Compatibility
The list of known compatible vehicles based on wiring diagrams available from Toyota North America. Compatibility and specific features can be determined by the presence of needed terminals in the DLC1 or DLC2 port.

DLC Ports
All compatible vehicles have a rectangular DLC1 port located in the engine bay. Some vehicles have an additional semi-circular DLC2 port in the passenger compartment. Both port types always have the VF1 terminal needed to read the OBD1 serial data stream.

DLC2 port vehicles
Most vehicles with a DLC2 port do not have the TE2 terminal in the DLC1 port to activate the serial data stream. On these vehicles, TE2 must be connected to E1 on DLC2 connector to read the OBD1 data stream from DLC1. The YODA OBD1 transmitter is available with a DLC2 cable but it requires that you add a 12v power supply to the Option B terminal of the DLC2 connector.

Using the YODA OBD1

1. Connect the YODA OBD1 to the DLC port prior to turning the key on.
2. When the key is turned on, the ECU will be in TE2 test mode.
   • OBD1 serial data stream is transmitted with DLC voltages (excluding voltage feedback values).
   • All Toyota documentation states that if TE2 mode is used, it must be activating prior to turning the vehicle on. If you use the app to turn TE2 mode off then back on, it may not behave as expected. TE1 mode can be turned on or off without impacting TE2 behavior.
   • If TE1 is activated, diagnostic trouble codes will be captured in addition to serial and DLC voltage values being displayed.

Test Modes
TE1 Off – TE2 Off	Read DLC values with engine in normal driving mode.
TE1 On – TE2 Off	Capture diagnostic trouble codes. Set standard ignition timing.
TE1 Off – TE2 On	Read OBD1 and DLC values.
TE1 On – TE2 On	Read OBD1 and DLC values. Capture diagnostic trouble codes. ECM is in high sensitivity mode.

OBD1 Data
Specific data available will depend on vehicle equipment and the functionality of the engine ECM. Fields unsupported by your vehicle can be hidden. Vehicle must have a DLC1 port with electrical terminals in the positions for VF1 and TE2. The data can be used to troubleshoot malfunctions. Sensors, wiring, connectors and the ECM’s interpretation of the sensors can be validated quickly and accurately. The values are updated approximately every 1.3 seconds.

Lexus & Toyota factory service manuals for 1994 & 1995 vehicles have a table titled "REFERENCE VALUE OF ECM DATA" that contains expected values, states and behaviors.

OBD1 Values

• Coolant Temperature
  • If the engine coolant temperature sensor circuit is open or shorted, the ECM typically assumes an engine coolant temperature value of 80°C (176° F).
• Throttle Position
• Air Measurement (MAF, MAP, VAF)
• Idle Air Control
• Injector Pulse
  • Duration of fuel injector pulse in milliseconds.
• Ignition Timing
• Engine Speed
• Vehicle Speed
• Target Air Fuel Mixture
  • This is similar to OBD2 fuel trim. It's how the ECM is attempting to alter the fuel delivery relative to the current state.

OBD1 Flags

• Warm Up mode
• Cold Start mode
• Idle Switch state
  • This switch on the TPS indicates when it is open.
• Acceleration Enrichment mode
• Current Air Fuel Mixture
  • Lean or Rich. Effectively a digital representation of upstream oxygen sensor reading.
• Closed/Open Loop mode
  • When the engine is at operating temperature and the engine is well above idle, the ECM goes into Close Loop Mode. Oxygen sensor readings are used as feedback to adjust fuel mixture levels.
• Switch states

DLC Voltages

• Oxygen Sensors 1 & 2
  • Measurements are taken directly from the sensors at 10 times the rate than the OBD1 data feed.
  • Electrical terminals for the sensors must be in the DLC1 port.
  • Sensor 2 is the second bank of a 6 or 8 cylinder engine with two upstream oxygen sensors.
  • Sensor 2 is sometimes the downstream sensor of 4 cylinder vehicles.
• Battery
  • Measured after main fuse, EFI fuse and EFI main relay.
  • Value at the terminal is typically 0.1 volt below actual battery voltage.
• Fuel Pump circuit
  • Measured after circuit opening relay and air flow switch(if equipped).
• Voltage Feedback 1 & 2
  • When in closed loop mode, the voltage indicates the feedback correction that is occurring as a result of the upstream oxygen sensor reading.
  • Some vehicles have 5 levels while others only have 3.
  • Voltage Feedback 2 is the second bank of a V6 engine.
  • VF1 terminal is used to transmit OBD1 serial data when in TE2 test mode. Therefore, voltage feedback values aren’t available when in TE2 test mode.
  • Voltage Feedback is equivalent to Target Air Fuel Mixture in OBD1 data stream

Fuel Mixture Charts
Fuel mixture data is easier to interpret when depicted on a chart rather than as a number.

• Above the center line represents rich, below represents lean.
• The black line indicates the oxygen sensor value.
  • The center line is 450mv.
  • Only useful when engine is hot and RPMs are high.
• When TE2 is activated, the colored background indicates if the engine is running rich or lean.
  • The OBD1 fuel mixture flag is the source of the data.
  • This should correlate with the oxygen sensor when the engine is hot and RPMs are high.
  • Data feed only contains two states.
  • Blue is rich. Orange is lean.
  • Oxygen sensor values are collected at 10 times the rate. The fuel mixture background will step each time that data is received. If a package is bad, no data will be displayed.
• When TE2 is not activated, the colored background indicates the feedback correction taking place.
  • The voltage feedback terminals (VF1, VF2) of the DLC1 connector are the source of the data.
  • Some vehicles have 5 levels while others only have 3.
  • Voltage feedback has a neutral state will not display any color on the chart.
  • Blue equates to increasing fuel delivery.
  • Orange equates to decreasing fuel delivery.
  • Some vehicles report a lean state (0v) when feedback correction is stopped (Idle switch on).
  • This value can be used to adjust the fuel mixture on vehicles with vane type AFMs that have an idle adjustment screw that is not sealed.

Data Link Connector terminals used by YODA OBD1
The location of terminals indicates where and what functionality is supported.

TE1	Test Mode 1. Capture diagnostic trouble codes. Set standard ignition timing.
TE2	Test Mode 2. Activates OBD1 data stream
VF1	Voltage feedback, bank 1. Serial data stream when TE2 is activated.
VF2	Voltage feedback, bank 2.
FP	Fuel Pump circuit.
OX1	Upstream oxygen sensor, bank 1.
OX2	Upstream oxygen sensor, bank 2 on six or eight cylinder engines with two upstream sensors. Downstream oxygen sensor on vehicles with downstream sensor and only one upstream sensor. Vehicle wiring diagram will determine expected behavior.
W	Warning light. Used to read trouble codes.

Data Link Connector terminals by vehicle
The following table contains the terminals in each DLC of supported vehicles.

Vehicles with DLC & OBD1
TOYOTA
Years	Model	Engine	DLC1	DLC2
1993-1995	4Runner	22R-E	TE1, TE2, VF1, FP, OX1, OX2, W
1993-1995	4Runner	3VZ-E	TE1, TE2, VF1, FP, OX1, OX2, W
1992-1993	Camry	3VZ-FE	TE1, TE2, VF1, VF2, FP, OX1, OX2, W	TE1, TE2, W, VF1
1992-1995	Camry	5S-FE	TE1, TE2, VF1, FP, OX1, OX2, W	TE1, TE2, W, VF1
1992	Celica	5S-FE	TE1, TE2, VF1, FP, OX1, W
1992-1993	Celica	3S-GTE	TE1, TE2, VF1, FP, OX1, W
1993-1995	Celica	5S-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1994-1995	Celica	7A-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1993-1995	Corolla	4A-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1993-1995	Corolla	7A-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1991-1992	Land Cruiser	3F-E	TE1, TE2, VF1, VF2, FP, OX1, OX2
1993-1994	Land Cruiser	1FZ-FE	TE1, TE2, VF1, VF2, FP, OX1, OX2, W
1993-1995	MR2	3S-GTE	TE1, TE2, VF1, FP, OX1, W
1993-1995	MR2	5S-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1995	Paseo (CA only)	5E-FE	TE1, TE2, VF1, FP, OX1, OX2, W
1993-1995	Supra	2JZ-GE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1
1993-1995	Supra Turbo	2JZ-GTE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1
1993	T100	3VZ-E	TE1, TE2, VF1, FP, OX1, OX2
1994	T100	3VZ-E	TE1, TE2, VF1, FP, OX1, OX2, W
1992-1995	Truck	3VZ-E	TE1, TE2, VF1, FP, OX1, OX2, W
1993-1995	Truck	22R-E	TE1, TE2, VF1, FP, OX1, OX2, W
LEXUS
Years	Model	Engine	DLC1	DLC2
1992-1993	ES 300	3VZ-FE	TE1, TE2, VF1, VF2, FP, OX1, OX2, W	TE1, TE2, W, VF1
1993-1995	GS 300	2JZ-GE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1
1990-1992	LS 400	1UZ-FE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1
1993-1994	LS 400	1UZ-FE	TE1, VF1, VF2, FP, OX1, OX2, W	TE1, TE2, W, VF1
1993-1995	SC 300	2JZ-GE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1
1992-1995	SC 400	1UZ-FE	TE1, VF1, VF2, FP, OX1, OX2	TE1, TE2, W, VF1

Vehicles with only DLC
TOYOTA
Years	Model	Engine	DLC1
1985-1992	4Runner	22R-E	TE1, VF1, FP, OX1
1989-1992	4Runner	3VZ-E	TE1, VF1, FP, OX1
1985-1988	Celica	3S-GE	TE1, VF1, FP, OX1
1986-1989	Celica	3S-GTE	TE1, VF1, FP, OX1
1987-1991	Celica	4A-FE	TE1, VF1, FP, OX1
1990-1991	Celica	3S-GTE	TE1, VF1, FP, OX1, OX2
1990-1991	Celica	5S-FE	TE1, VF1, FP, OX1
1992-1993	Celica	4A-FE	TE1, VF1, FP, OX1, W
1990-1992	Corolla	4A-FE	TE1, VF1, FP, OX1
1990-1992	Corolla	4A-GE	TE1, VF1, FP, OX1
1988-1990	Land Cruiser	3F-E	TE1, VF1, VF2, FP, OX1, OX2
1990-1992	MR2	3S-GTE	TE1, VF1, FP, OX1
1990-1992	MR2	5S-FE	TE1, VF1, FP, OX1
1991-1992	Paseo	5E-FE	TE1, VF1, FP, OX1
1993-1995	Paseo	5E-FE	TE1, VF1, FP, OX1, W
1986-1990	Supra	7M-GE	TE1, VF1, FP, OX1
1986-1990	Supra	7M-GTE	TE1, VF1, FP, OX1
1991-1992	Supra	7M-GE	TE1, VF1, FP, OX1, W
1991-1992	Supra	7M-GTE	TE1, VF1, FP, OX1, W
1991-1992	Tercel	5E-FE	TE1, VF1, FP, OX1
1993-1995	Tercel	5E-FE	TE1, VF1, FP, OX1, W
1985-1992	Truck	22R-E	TE1, VF1, FP, OX1
1989-1991	Truck	3VZ-E	TE1, VF1, FP, OX1