OBDII Archives - UnderhoodService
Ignition Coil Output

To see inductance inside the primary windings, use an amp probe placed around the positive wire for the ignition coil.

Diagnosing Misfires

What if there are no codes and a misfire is intermittent? This is where it gets complicated.

Diagnostic Procedures For Stop/Start Systems

Stop/start technology is more than just a switch wired to the brake pedal and starter.

OBDII Connectors

OBDII connectors serve as the main communication point between the technician and the vehicle.

ECM Damage

Engineers have devised two strategies that can be called the “immune system” for the electrical system.

Watch: OBD Zero Diagnostics in an OBDII World

Follow along as we discuss the latest OBDII engine management systems. Sponsored by Summit Racing Equipment.

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.

Oxygen Sensor And Catalyst Efficiency

The catalyst efficiency monitor verifies the catalytic converter is operating at a high enough efficiency rating to keep exhaust emissions within the predetermined values. The PCM compares the signals from the upstream and downstream oxygen sensors to determine the state of the converter. These “tests” are called the readiness monitors. 

Fencing In Vehicle Networks: Discussing Cybersecurity Best Practices On The Horizon

Shortly, you will see cars in your bays that have the ability to communicate with one another. These cars are already on the street, and can facilitate driver access to potentially dangerous networks.

Volumetric Efficiency Diagnostics

A few years ago, I obtained an OBDII scan tool/dynamometer simulation/calculation program that can graph volumetric efficiency (VE) over rpms. Using real world vehicles, and no useful instructions, I devised a test sequence that allows a technician to see things another way. What is Volumetric Efficiency? Let’s keep this simple to start. An engine is