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An OBD2 (SAE J1962) connector has 16 pins: pins 4 and 5 are chassis and signal ground, pin 16 is battery positive (12 V), pins 6 and 14 are CAN-H and CAN-L, and pins 7 and 15 are the ISO 9141/14230 K-line and L-line. Only pins 4, 5, 7, and 16 are common to all vehicles.
The table lists each of the 16 connector pins with its standard function and typical idle voltage. Voltages are measured with the ignition on and the bus idle, so active data traffic will show different readings.
Typical idle voltage by OBD2 connector pin
| Pin | Function | Typical idle voltage (V) | Notes |
|---|---|---|---|
| 1 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 2 | SAE J1850 PWM bus positive | 5 | Active signal line, toggles 0-5 V |
| 3 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 4 | Chassis ground | 0 | Direct body ground |
| 5 | Signal ground | 0 | Logic reference ground |
| 6 | CAN-H (ISO 15765-4) | 2.5 | Recessive idle; rises when dominant |
| 7 | ISO 9141-2 / ISO 14230-4 K-line | 12 | Idle high, pulled to ground for data |
| 8 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 9 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 10 | SAE J1850 PWM bus negative | 5 | Active signal line, toggles 0-5 V |
| 11 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 12 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 13 | Manufacturer reserved | 0 | Not defined by SAE J1962 |
| 14 | CAN-L (ISO 15765-4) | 2.5 | Recessive idle; falls when dominant |
| 15 | ISO 9141-2 / ISO 14230-4 L-line | 12 | Optional; used mainly at initialization |
| 16 | Battery positive | 12 | Always live, fused at about 4 A |
- Ground or power pin present on all vehicles
- Data bus pin used by one or more common protocols
- Optional pin, not fitted on all vehicles
- Reserved or manufacturer-specific pin
Voltages are typical idle levels with ignition on; active bus traffic changes the readings.
- The OBD2 connector uses 16 pins in two rows of 8, per SAE J1962.
- Pin 16 is battery positive, typically 12 V, and pin 4 is chassis ground.
- CAN-H (pin 6) and CAN-L (pin 14) idle recessive at about 2.5 V each.
- Pins 2 and 10 carry SAE J1850 PWM, used mainly on older Ford vehicles.
- Only pins 4, 5, 7, and 16 are required on every OBD2 vehicle.
How Do You Read an OBD2 Port Pinout Chart?
An OBD2 port pinout chart maps each of the 16 connector pins to its function, so you can identify a wire or test a circuit without guessing. The connector follows SAE J1962, with pins arranged in two rows of 8.
Step by Step
- Read the Pin column first. Numbers 1 through 16 identify the physical terminal positions; odd and even numbers sit on opposite rows.
- Check the Function column. It names the protocol or role for each pin, such as CAN-H on pin 6 or K-line on pin 7.
- Use the voltage column as a reference. It shows the typical idle level with the ignition on and the engine off, measured relative to chassis ground.
- Treat the Notes column as context. It flags manufacturer-reserved pins and optional lines such as the L-line on pin 15.
The three values worth memorizing are 12 V on pin 16 (battery positive), 0 V on pins 4 and 5 (grounds), and about 2.5 V on pins 6 and 14 (recessive CAN idle). Only pins 4, 5, 7, and 16 are common to all vehicles, so a dead reading on any other pin is not automatically a fault.
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What Changes the Values on an OBD2 Port Pinout Chart?
The voltages and states listed on an OBD2 port pinout chart describe a reference condition, not a live snapshot of every vehicle. Real readings shift because the chart assumes the ignition is on, the engine is off, and the bus is idle. The factors below keeps your measurements comparable to the published values.
Ignition and Engine State
Pin 16 stays at battery positive near 12 V whenever the connector is live, but the data pins only behave as charted once the ignition is on. With the engine running, system voltage rises toward the alternator output, so pin 16 reads higher than the nominal 12 V figure.
Bus Activity and Module Wake-Up
CAN-H and CAN-L idle recessive at about 2.5 V each only when the network is quiet. Any module transmitting drives dominant bits, pulling CAN-H toward 3.5 V and CAN-L toward 1.5 V, so a busy bus shows averaged values that drift from the idle figure.
Measurement Method and Meter Loading
A high-impedance digital meter reads the idle levels accurately, while a low-impedance test light or analog meter can load a signal line and drag the reading down. Probing the wrong reference, such as signal ground instead of chassis ground, also offsets every value you record.
Age, Wiring and Temperature
Corroded terminals and aged harnesses add resistance that lowers the voltage seen at the pins, especially on ground pins 4 and 5. Temperature extremes shift semiconductor and bus behavior slightly, so readings taken on a cold morning may differ from those at operating temperature.
What Are the Most Common OBD2 Port Pinout Chart Mistakes?
Most errors with an OBD2 port pinout chart come from assuming all 16 pins are standardized when only pins 4, 5, 7, and 16 are common to every vehicle. The chart defines connector functions, not whether a specific vehicle actually populates a given pin.
Mistakes to Avoid
- Probing reserved pins. Pins 1, 3, 8, 9, 11, 12, and 13 are manufacturer reserved and undefined by SAE J1962, so their function varies by vehicle. Verify the vehicle’s own wiring information before connecting anything to them.
- Confusing the two grounds. Pin 4 is chassis ground and pin 5 is signal ground, and they serve different purposes. Use pin 4 for power-related checks and pin 5 as the logic reference.
- Misreading CAN idle voltage. CAN-H on pin 6 and CAN-L on pin 14 both idle recessive at about 2.5 V, which can look like a fault to someone expecting 0 V or 5 V. Treat 2.5 V on both lines as normal until data is exchanged.
- Assuming the L-line is always present. Pin 15 carries the optional ISO 9141-2 or ISO 14230-4 L-line and is not fitted on every vehicle. Confirm the protocol before diagnosing a missing signal there.
- Ignoring pin 16’s live feed. Pin 16 is battery positive at about 12 V and stays live, fused at roughly 4 A. Disconnect the battery or pull the circuit fuse before working near the connector.
Notes & Assumptions
- Values follow the SAE J1962 connector standard and the common OBD2 protocols (SAE J1850 PWM/VPW, ISO 9141-2, ISO 14230-4, ISO 15765-4 CAN).
- Voltages are typical idle levels measured with the ignition on and the engine off, relative to chassis ground.
- CAN-H and CAN-L are shown at their recessive idle level of about 2.5 V; during dominant bits CAN-H rises toward 3.5 V and CAN-L falls toward 1.5 V.
- Pins 1, 3, 8, 9, 11, 12, and 13 are manufacturer-specific and are shown as 0 V because they are undefined by the standard.
- The L-line on pin 15 is optional and is not fitted on all ISO 9141-2 or ISO 14230-4 vehicles.
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Bottom Line
An OBD2 port pinout chart is most useful when you memorize the four pins every vehicle must have: 4 (chassis ground), 5 (signal ground), 7 (K-line), and 16 (battery positive, 12 V). If a scan tool powers up but cannot communicate, checking pin 16 for 12 V and pins 4 and 5 for ground is the fastest first step. All other pins, including CAN-H on 6 and CAN-L on 14, depend on the protocol the vehicle actually uses.
Frequently Asked Questions about OBD2 Port Pinout Chart
How do I read an OBD2 port pinout chart?
Read the chart by matching each numbered pin to its function, starting with the 16 pins arranged in two rows of 8 per SAE J1962. Pins 4 and 5 are grounds, pin 16 is battery positive, and the remaining pins carry specific protocols, so confirm the protocol before probing.
What voltages should I expect on the OBD2 connector pins?
Expect about 12 V on pin 16, 0 V on pins 4 and 5, and about 2.5 V idle on CAN-H (pin 6) and CAN-L (pin 14). The K-line on pin 7 idles near 12 V, while manufacturer-reserved pins are undefined by the standard.
Which OBD2 pins are the same on every vehicle?
Only pins 4, 5, 7, and 16 are required on every OBD2 vehicle. Pin 4 is chassis ground, pin 5 is signal ground, pin 7 is the K-line, and pin 16 is battery positive, so other pins may be empty or manufacturer-specific.
What is the safe voltage limit when probing OBD2 pins?
Keep probe voltages at or below battery level, about 12 V, and never apply external power to signal pins. Use a high-impedance meter and back-probe carefully, because feeding voltage into CAN or K-line pins can damage the vehicle modules.
Why do CAN-H and CAN-L both read about 2.5 V at idle?
Both CAN lines sit at roughly 2.5 V in the recessive idle state, so a meter shows nearly the same value on pins 6 and 14. During dominant bits CAN-H rises toward 3.5 V and CAN-L falls toward 1.5 V, which a simple meter averages out.
What are common mix-ups when using an OBD2 pinout chart?
A common mix-up is confusing pin 4 chassis ground with pin 5 signal ground, or assuming pins 2 and 10 are CAN when they carry SAE J1850 PWM. Also note that pin 15 L-line is optional and not fitted on all ISO 9141-2 or ISO 14230-4 vehicles.