Key takeaways

  • Choose Bluetooth Low Energy: iPhones can’t connect to classic-Bluetooth OBD readers.
  • Permanent codes and since-clear counters are what catch a reset check-engine light.
  • A dealer tool should be read-only unless someone deliberately confirms a clear.
  • Speed matters on a busy lot, so look for full CAN support and software that asks for many readings at once.
  • Know the limits: generic OBD-II reads engine and emissions systems, not ABS or airbags.

Why does Bluetooth Low Energy matter for iPhone?

Many inexpensive OBD-II readers use “classic” Bluetooth. Android phones can talk to them, but iPhones only let apps connect to classic-Bluetooth accessories built under Apple’s accessory program, which these readers aren’t. The fix is a reader that uses Bluetooth Low Energy, which iPhone and Android apps can both use.

  • Read the box carefully. Look for “BLE”, “Bluetooth Low Energy” or explicit iPhone support. A Bluetooth version number alone doesn’t guarantee the reader uses Low Energy.
  • Wi-Fi readers do work with iPhones, but the phone joins the reader’s Wi-Fi network while you scan, which is clumsy when you also need data on the lot.
  • Laptops. Chrome and Edge support Web Bluetooth, so a web app can scan from a laptop. Safari doesn’t.

If your team uses a mix of iPhones and Android phones, BLE is the only option that works for everyone.

Which codes should a dealer scanner read?

  • Stored codes (Mode 03): confirmed faults, the ones that turn on the light.
  • Pending codes (Mode 07): faults detected once but not yet confirmed. Often the first sign of a problem coming back after a clear.
  • Permanent codes (Mode 0A): faults a scan tool can’t erase. Supported on most vehicles from about the 2010 model year on.
  • Every responding module. On modern vehicles both the engine and transmission computers can answer; a scanner that shows only the first reply can miss a transmission code.
  • Freeze frame (Mode 02): the engine conditions when a code set, useful for judging how serious it is.

Plain-English descriptions matter too. “P0171” means nothing to a customer; “system too lean, bank 1” with a likely cause and cost range does.

Why are readiness monitors and since-clear counters essential?

This is the feature that separates an appraisal scanner from a code reader. Readiness monitors (Mode 01, PID 01) show which self-tests have finished. The since-clear counters show how far and how long the car has run since codes were last cleared: distance (PID 31), warm-ups (PID 30) and minutes (PID 4E). Distance and time with the light on (PIDs 21 and 4D) show how long a fault has been ignored.

Read together, they reveal a check-engine light that was cleared on the way to your lot. The best tools don’t just print the numbers; they turn them into a verdict, such as “Codes cleared 38 km ago”. Our guide on spotting recently cleared codes explains how to read them.

What else should the scanner read?

  • Engine computer VIN (Mode 09). A mismatch with the car’s VIN points to a swapped computer.
  • Odometer from the engine computer (PID A6), on newer vehicles that support it, to compare with the dash.
  • Battery voltage. Under about 12.2 V with the engine off, or 13.2 V running, deserves a battery or charging-system check.
  • A live snapshot: RPM, coolant temperature and fuel trims. Large fuel trim corrections hint at vacuum leaks or fuel delivery problems.
  • Total engine run time where the vehicle reports it. On work trucks, high hours against low km means heavy idling.

How fast should a scan be?

OBD-II vehicles use one of five protocols: SAE J1850 PWM, J1850 VPW, ISO 9141-2, ISO 14230-4 (KWP2000) and ISO 15765-4 (CAN). Nearly every vehicle from about 2008 on uses CAN, which is fast, while older protocols are slower by nature. A good setup supports all five but tries CAN first, remembers which protocol each vehicle uses, and asks for several readings in one request instead of one at a time.

Reader quality matters as much as software. Low-cost clones with copied firmware can drop responses or misreport them, which shows up as slow scans and odd results. On a busy lot, a scan that finishes while you are still writing down the km gets used on every car; one that takes minutes gets skipped.

Should a dealer scanner clear codes?

Rarely, and only on purpose. Clearing codes erases the freeze frame and resets the monitors, which destroys exactly the evidence an appraisal relies on, and a car that leaves your lot with freshly cleared codes looks suspicious to the next buyer. A dealer scanner should be read-only by default, with clearing behind a deliberate confirmation for after a verified repair.

What hardware details matter on a lot?

  • Low profile. The port is usually under the dash near the driver’s knees; a bulky reader gets kicked.
  • Auto-sleep with low standby draw, in case one gets left plugged in overnight.
  • A status light so you can see it has power and is connected.
  • One reader per appraiser, labelled and registered to the dealership, plus a spare.

What can’t a generic OBD-II scanner do?

Generic OBD-II is the standard set of engine and emissions data every 1996-and-newer vehicle with the port must provide. It doesn’t read ABS, airbag, body or tire-pressure modules, which need manufacturer-level diagnostics. Electric and hybrid support is partial: battery health on most EVs needs manufacturer-specific data. And no scan replaces a mechanical inspection or a test drive.

How does Appraise handle scanning?

Appraise’s OBD scanner works with BLE readers on iPhone and Android, and in Chrome or Edge on a laptop. It reads all of the above, shows a verdict banner first, flags a recent clear in red, and prices each code from book labour hours at your own labour rate. Free Bluetooth OBD reader with your 14-day trial for the first 25 dealerships, anywhere in Canada; book a demo to claim one.

Key facts

  • iPhones can’t connect to classic-Bluetooth OBD readers; a Bluetooth Low Energy (BLE) reader works with iPhone and Android.
  • Permanent codes (Mode 0A) are supported on most vehicles from about the 2010 model year on.
  • Since-clear counters: PID 31 (km), PID 30 (warm-ups) and PID 4E (minutes).
  • OBD-II uses five protocols; nearly every vehicle from about 2008 on uses CAN (ISO 15765-4).
  • Web Bluetooth works in Chrome and Edge, not Safari.
  • Generic OBD-II covers engine and emissions only, not ABS, airbag or body modules.

Frequently asked questions

Do I need an expensive professional scan tool for appraisals?

Not for appraising. A good BLE reader with software built for appraisals covers powertrain codes and cleared-code detection. Manufacturer-level tools belong in the service bay, for diagnosing ABS, airbag and body systems.

Will any inexpensive OBD-II reader work?

On Android, most will connect. On iPhone, only Bluetooth Low Energy models will. Quality varies widely; clones with copied firmware can be slow or unreliable.

Can I leave the reader plugged in?

Unplug it after each appraisal. Even with auto-sleep, a reader draws a little power, and on a dealer lot it should move from car to car anyway.

Does generic OBD-II work on diesel pickups?

Yes, on light- and medium-duty diesel pickups with the standard port. Diesel vehicles report their own monitors, such as the particulate filter and NOx aftertreatment. Very heavy commercial trucks often use a different diagnostic standard.

What about electric vehicles?

Support is partial. EVs have no engine codes to read, and battery state of health usually needs manufacturer-specific data that generic OBD-II doesn’t provide.