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.)
Checking into Mode $06
Mode 06 is the actual system test data that OBD II looks at when it decides to set a pending code or a current fault code. If the test data is within the limits established by the vehicle manufacturer, the item gets a PASS and no codes are set. But if a value is out of range, OBD II flags it with a FAIL and keeps an eye on the component until the system monitor has run at least twice. Then, if the problem is still there, a DTC is set and the MIL light comes on.