Products suited to this guided test*
  • PicoBNC+ resistance test lead

  • *At Pico we are always looking to improve our products. The tool used in this guided test may have been superseded and the product above is our latest version used to diagnose the fault documented in this case study.

Charger-vehicle proximity line resistance (type 1)



The information on this page is illustrative. It is not to be used for training purposes or as guidance or instruction. It is also incomplete. A full version of this content can be found in our PicoScope 7 Automotive software, which is downloadable from here.



The purpose of the test is to check the operation and integrity of the Proximity Pilot (PP) line on an Electric Vehicle (EV) having a Type 1 coupling (IEC 62196-2) with the Electric Vehicle Supply Equipment (EVSE).

Further information

The PP line comprises a circuit designed to indicate to the OBC the connection status of the EVSE charging cable.

A connection is made between the vehicle and EVSE by pushing a Type 1 charging cable connector into the vehicle's charging port.

The two are disconnected by:

  1. Depressing a button on the Type 1 charging cable connector, which releases the connector and signals to the vehicle's On-Board Charger (OBC) to stop charging.
  2. Removing the charging cable connector from the vehicle's charging port.

The PP line functionality can be checked by disconnecting the PP line between the OBC and the vehicle charging port and measuring the change in resistance between the PP line (on the vehicle charging port side of the connector) and the vehicle chassis earth.

To complete this test you may need to disconnect connections at the OBC end of the circuit or locate a more accessible connector using the manufacturer's technical information.

In all circumstances, do not carry out a resistance measurement with the Proximity Pilot line intact as there is the potential for harm to the vehicle or your test equipment.

The modes of PP line operation for each connection status are described as follows:

  • With the EVSE charging cable and vehicle disconnected, the PP line circuit comprises a single path to chassis earth via a 2.7 kilohm resistor in the vehicle charging port, hence the measured resistance is 2.7 kilohms.
  • With the EVSE charging cable and vehicle connected, an additional path to chassis earth is created and the PP line circuit becomes two parallel paths to earth, with one path having a resistance of 150 ohms and the other 2.7 kilohms. The total resistance of the parallel circuit is 1/(1/150 + 1/2700) ohms = 142 ohms.
  • With the EVSE charging cable and vehicle connected and the Type 1 connector button depressed, the path to chassis earth is again two parallel paths to earth but with one path having a total resistance of 480 ohms (150 ohms + 330 ohms) and the other 2.7 kilohms. The total resistance of the new parallel circuit is 1/(1/480 + 1/2700) ohms = 408 ohms.

Symptoms and fault diagnosis

If the charging does not start when the EVSE charging cable is connected to the vehicle, there may be a high resistance in the PP line circuit within the charging cable connector. This is because the OBC expects to see approximately 142 ohms on this line before it commands, via a separate circuit, the EVSE to start charging.


This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

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Guided test: Charger-vehicle proximity line resistance (type 1)