OBD II Archives - UnderhoodService
Freeze Frame Diagnostics

Freeze frame data is a “snap shot” of when the code occurs of the specific sensor PIDs.

Oxygen Sensor Questions Answered

If an O2 sensor is not reading properly or is borderline, it should be replaced regardless of its age or mileage.

VIDEO: Blending Service Information Sources

Finding P0420 on a specific vehicle can be researched using blended service info. This video is sponsored by Mitchell 1.

The Fight For The OBDII Port

Some techs have noticed coverage on some newer vehicles is not that great, they can’t access modules or tests are missing.

OBD II Emissions Monitors

OBD II is primarily emissions-driven and will set codes anytime a vehicle has a fault that may cause emissions to exceed federal limits by 1.5 times. It doesn’t necessarily mean the vehicle has a real emissions problem. Many times it does not. But, if the nature of the failure is such that it might cause emissions to rise, OBD II will set a code anyway. That is why some states are allowing motorists to opt for a second-chance tailpipe test if their vehicle fails an OBD II test. In many instances, the vehicle will pass the tailpipe test.

OBDII Code Guide

OBDII standardized the codes and emission monitors for vehicles. The structure or nomenclature can be read by technicians by looking at the single letter and four digits to determine what the codes mean.

OBD1 Diagnostic Challenges

The real challenge is staying current, but still having a working knowledge of the older OBD1 diagnostic procedures. After all, you never know when a 1984 Buick may roll into your service bay and you’ll need to pull out your magic paper clip.

obd1 diagnostics featured
Think Before You Grab The Scanner

Scott “Gonzo” Weaver tells the story of what can happen when you forget the basics as a technician.

Port of Opportunity

There is a flood of aftermarket OBD-II devices that are designed to track drivers, diagnose check engine lights, and even perform remote starting, but are they good for the aftermarket?

Making Money with Mode $06

Nothing is more frustrating than “fixing” a customer’s vehicle and then have it come back a few days or weeks later with the check engine light on and the same fault code or a new fault code. You look bad, lose your customer’s confidence in your ability to fix their vehicle, and in states that

Mode 06 diagnostics
Top Ten Fuel Pump Fails

10. Strainer Blocks Fuel-Level Sender A fuel pump inlet strainer may be installed that is interfering with the travel of the fuel-level sensor’s float arm, which causes an optimistic fuel level reading. Dented fuel tanks may also cause a false reading by pushing the fuel-level sensor and fuel pump inlet filter above the remaining fuel

fuel pump failure
20 Years of OBDII Connection

In 1994, select Toyota, GM and Ford models were sold with OBDII emission systems. To the amazement of many technicians, all of these models came with the same ­diagnostic connector called the data link connector or DLC. In 1995, 40 percent of vehicles sold had a common DLC. By the 1996 model year, all vehicles

OBDII connector