VW ID.3 and ID.4: what diagnostics looks like on the MEB platform

The ID.3 and ID.4 sit on MEB, a platform designed for electric vehicles rather than adapted from a combustion one. That changes the diagnostic picture fundamentally.

Related: OBD on electric vehicles, what it gives.

Why generic OBD-II gives so little

OBD-II is an emissions standard. Its entire mandated content is combustion data: misfires, fuel trims, oxygen sensors, catalyst efficiency, EVAP integrity.

An electric vehicle has none of that. There is nothing for the standard to require, so nothing is required.

Everything that matters here — traction battery state of health, cell voltages, inverter data, thermal management, charging diagnostics — is manufacturer-specific by definition.

Scan tool limits: what OBD cannot see and electric vehicle OBD battery diagnostics.

The 12 V battery: still the most common failure

Worth stating first, because it surprises people.

An electric car still has a conventional 12 V battery, and it powers the contactors and control modules that decide whether to connect the traction battery at all.

A flat 12 V battery immobilises the vehicle completely, regardless of a full traction battery. It is among the most common roadside calls for electric vehicles generally.

This is readable with a standard adapter, and it is the single most valuable thing generic diagnostics offers here.

EV 12V battery failures and P0560 to P0563 system voltage faults.

Software, and the early-car caveat

The ID range launched with software that was widely criticised, and Volkswagen has issued substantial updates since — including over-the-air on later cars.

Practical consequences:

• Establish the software version on a used example, and whether updates have been applied.
• Behaviour can change between updates, which is unfamiliar to most car owners.
• Early cars may require a workshop visit for updates rather than receiving them over the air.

OTA firmware updates and diagnostics and UN R155 and R156 vehicle cybersecurity.

Battery health, and how to assess it

The number that determines a used electric car’s value, and generic OBD-II will not give it to you.

What you can do:

• Charge to 100% and compare the indicated range against the original figure for that battery size.
• Watch charging taper at a fast charger — how quickly the rate falls off is informative.
• Measure consumption over a known route in known conditions.
• Ask for a manufacturer battery health report, which dealers can produce.

Used EV buying, battery health check and hybrid battery state of health monitoring.

Euro 7 introduces battery durability reporting requirements, which should make this considerably more transparent on newer vehicles: Euro 7 and on-board monitoring.

Thermal management

Electric vehicles depend on keeping the battery within a temperature window, for both performance and longevity.

Signs of trouble: reduced charging speed, reduced regenerative braking, coolant pumps audible at unusual times, or range varying more than weather explains.

Everything mechanical is conventional

And no scan tool diagnoses any of it.

• Tyres wear faster — weight and instant torque: tyre rotation and wear patterns and inner edge tyre wear.
• Brakes corrode rather than wear, because regeneration does most of the slowing. Seized calipers from disuse are far more common than worn pads: grinding when braking and clunk when braking.
• Suspension carries more weight: suspension bushes wear symptoms.
• Vibration diagnosis is identical to any car: car shakes at motorway speed.

The brake point deserves emphasis. On a car driven mostly with regeneration, brakes fail from lack of use rather than from wear — and that is not intuitive.

Buying used

1. Indicated range at 100% against the original specification.
2. Charging taper at a fast charger.
3. Software version and update history.
4. 12 V battery age — it strands more electric cars than anything else.
5. Brakes, specifically for corrosion and seized calipers.
6. Tyres, which wear faster and are expensive in EV-specific sizes.
7. Service history, which for an EV is shorter but not absent.

Try it on the free tier of the app — pair an ELM327 adapter and check 12 V system voltage. On an electric vehicle that is the reading most likely to strand you, and the one generic diagnostics handles best.