OBD II Archives - Page 4 of 5 - Brake & Front End
Foreign Affairs: VW P Codes — … Putting Out The MIL

After 10-plus years of dealing with OBD II, it should be apparent that we are on a learning curve that probably has no end. Almost daily we have a Volkswagen model come into the shop with a check engine light on, or a “state OBD II failure” form. Although we have the latest scanner software

Maintenance Essentials…, OBD II & Chassis Checks

All cars need maintenance. The fact is mechanical devices wear and fail in normal use, and deteriorate over time, so being able to diagnose a future failure has become a part of the automotive repair and service industry. Customers always ask how long it will be before a component will fail, and are usually not

Diagnostic Dilemmas: Symptom Diagnosis…The Journey Begins

When I first began my automotive career way back in 1957, the symptoms of an ailing engine were very apparent. A carburetor with a worn accelerator pump, for example, would characteristically stumble on acceleration and a closed-up set of distributor contact points would cause the engine to become very sluggish. Low fuel pressure caused by

When Should You Replace an Oxygen Sensor?

Is there a mileage or time requirement for oxygen sensor replacement? Simple answer: No. Oxygen sensors were first used for fuel trim and emissions in the late 1970s and into the mid 1990s. A single sensor was installed into the exhaust stream to modify fuel delivery and maintain catalytic converter efficiency. Beginning January 1, 1996,

Troubleshooting MIL Issues: OBD II & “CAN” Scan Tool Diagnostics

The Malfunction Indicator Lamp (MIL) is one of the most misunderstood warning lights on vehicles today. Most motorists have no idea what the light means or why it’s on. Some think the MIL light is an oil change reminder light. Others realize something must be amiss to cause the light to come on, but don’t

Up in Vapor

Gasp! It’s the “Gas Cap Code”! Oh no, you just pulled a code P0422, evaporative purge small leak detected… Here goes the needle in the haystack syndrome. So what do you do? Recommend a new gas cap and ship it? Well you could do that, but would that be in your or your customer’s best

Diagnostic Dilemmas: The Pressures of Intake Manifold Vacuum Tests

Several years ago, a retired school teacher brought in a 1994 Chevrolet S-10 Blazer that had developed an intermittent rough idle condition. Although a rebuilt engine had been installed a year before, and all of the wiring and vacuum hoses looked as if they were in factory condition, I took nothing for granted. An ignition

Codes & Converters

It is a moral dilemma that many shops encounter on a regular basis. It starts when a good customer comes in with the engine light a blaze. Running your usual diagnostics, you encounter a catalytic converter efficiency code, slow to responded oxygen sensor or some proprietary fuel trim code. Other than the light, the customer

Diagnostics Through CAN Networks

Since model year 2003, a growing number of domestic and import vehicles have been built with a new onboard communications protocol called CAN (Controller Area Network). CAN is essentially an engineering standard for how computers and modules talk to one another via the serial data bus in a vehicle’s wiring system. It’s a high speed

VW OBD II Revisited: Good Vehicle Service History Helps Determine Causes of Repeat Failures

After 10-plus years of dealing with OBD II, it should be apparent that we are on a learning curve that probably has no end. Almost daily we have a VAG model come into the shop with a check engine light on, or a “state OBD II failure” form. Although we have the latest scanner software

Replacing Oxygen Sensor: Saving the Environment and Your Customer’s Catalytic Converter

The oxygen (O2) sensor is the master switch in the fuel control feedback loop. The sensor monitors the amount of unburned oxygen in the exhaust and produces a voltage signal that varies from about 0.1 volts (lean) to 0.9 volts (rich). The computer uses the O2 sensor’s signal to constantly fine tune and flip-flop the

OBD II Diagnostics: Checking into Mode $06

In this scan tool diagnostics article, we take a look at Mode $06 functions which govern non-continuous monitors (EVAP, catalyst, EGR, etc.)