Tag Archives: OBD SCAN

Computer Diagnostics for Your Vehicle is a Vital Service

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When an auto repair shop recommends a ‘computer diagnosis’ it sounds serious, and everyone knows that serious vehicle problems can lead to serious repair bills. However, AAA experts advise consumers not to be overly concerned because computer diagnosis is a common practice for identifying problems on today’s microprocessor-controlled cars.

 

 

“If your vehicle needs a computer diagnosis, don’t be alarmed. This is often the most efficient and cost effective way for an automotive technician to diagnose a problem,” says John Nielsen, director, AAA Automotive Engineering and Repair. “Just be sure to have the repair facility explain what will be done before you authorize the work because ‘computer diagnosis’ is a generic term that can cover a wide range of operations.”

 

  • Modern vehicle electronic control systems “know” and monitor the operating parameters of every component. When the Powertrain Control Module (PCM) that manages the system sees a signal that is outside normal limits, or fails to see an expected change in a signal, it stores a Diagnostic Trouble Code (DTC).

 

  • To access DTCs, technicians connect a “scan” tool to a Diagnostic Link Connector that is commonly located under the driver’s side of the instrument panel. The scan tool displays any stored codes, but that is only the beginning of a full computer diagnosis.

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  • DTCs don’t tell a technician if a particular part is bad, they only indicate that the PCM has seen something it didn’t expect in a certain circuit. The problem might be the part, but it could just as easily be an issue with the circuit’s electrical wiring.

 

  • Sometimes, DTCs are set when there is nothing wrong with the electronic control system. This happens when a mechanical problem, like an engine vacuum leak, creates operating conditions that cause system components to generate signals outside their normal range.

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  • To pinpoint a problem, the technician starts with the DTC, then performs additional tests. These can range from mechanical checks, like engine compression, to in-depth electronic diagnosis. One common procedure uses special test equipment to access the electronic control system data network and monitor real-time signals from the system components.

 

The ability of technicians to determine what additional tests are needed, and to accurately interpret both test results and computer network data, comes from extensive training and experience. Today’s technicians use vehicle computer diagnosis in much the same way surgeons employ medical testing. In both cases, combining test results with expert knowledge and skilled hands can lead to an accurate diagnosis and an ultimate cure.

 

 

Emission Testing in Texas

Emission Testing

Emission Test Check List Mechanic Car Engine

Emission Testing Information
The type of emission test for your vehicle is determined by your location and the age of the vehicle.  The information below outlines the criteria, and provides a link to detailed information about the specific emission tests.

 

Houston/Galveston Area Motorists
1995 and older vehicles will receive the Accelerated Simulation Mode (ASM) test, while 1996 and newer vehicles receive the On-Board Diagnostic (OBDII) test.

 

On Board Diagnostics Plug Car and Truck

 

What is ASM2 and how does it work?


This test uses a dynamometer, which measures emissions under simulated driving conditions. In a sense, it’s like a treadmill stress test for your vehicle. This tailpipe test is a cost-effective way to get very accurate, realistic results. A vehicle will fail the test if there is an excessive amount of Hydrocarbon, Carbon Monoxide or Oxides of Nitrogen.

 

Please note that 4 wheel drive vehicles will continue to receive the current Two-Speed Idle test. If your vehicle fails the ASM test, you can return to the same public inspection station within 15 days of your initial test for a free retest.

 


Two Speed Idle Test

 
The Two-Speed Idle test is a tailpipe emissions test. This means the analyzer measures exhaust emissions directly from the vehicle’s tailpipe with the engine idling at a high and then low speed. TSI measures most of the common factors contributing to the formation of lung damaging ground level ozone.

 

A vehicle will fail the test if there are excessive amounts of hydrocarbons or carbon monoxide. TSI is used for older vehicles that are not equipped with the advanced on-board diagnostic computer system.

 


 

 

Reasons Why A Vehicle May Fail the ASM2 Test

Excessive Hydrocarbons (HC):

 
High hydrocarbon emissions result when fuel in the engine does not burn completely. HC in the presence of oxides of nitrogen (NOx) and sunlight may form ground-level ozone, a major component of urban smog.

 

Check the following:

  • Internal Engine Problems
  • Faulty Air Pump
  • Ignition System
  • Exhaust Gas Recirculation System (EGR)
  • Catalytic Converter
  • Gas Cap

 

Excessive Carbon Monoxide (CO):
A rich fuel mixture can cause high amounts of carbon monoxide, which can occur when there is too much or too little air reaching the combustion chamber.

 

Check the following:

  • Misadjusted Carburetor
  • Faulty Fuel Injection System
  • Worn Rings/Valve Guides
  • Air Pump System

fuel-injectors-the-shop-in-alvin-auto-repair

 

Excessive Oxides of Nitrogen (NOx):
High NOx can occur when there is excessive temperature in the combustion chamber or a damaged catalytic converter.
Check the following:

  • Air Injection System
  • Exhaust Gas Recirculation System (EGR)
  • Combustion Chamber Deposits
  • Oxygen Sensor
  • Catalytic Converter

brazoria-county-emission-testing-obd 2 -and-asm-testing

 

Diagnostics for NOx failures

OVERALL
Check for causes of high combustion temperatures. Primary systems that affect NOx include:

  • Mixture control (lean)
  • EGR
  • Ignition
  • Check Catalytic Converter

 

1981-86
Check the following:

  • O2 sensor (The signal from the O2 Sensor provides a wealth of information on how the vehicle is running.)
  • EGR valve and EGR hose
  • Ignition timing and system (advanced timing and ignition components are some of the most common problems)
  • Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
  • Catalytic converter
  • Primary feedback sensor failure, including oxygen sensor, MAP/MAF, TPS, RPM, and CTS sensors

 

1987-95
Check the following:

  • Use OBD, if available
  • O2 sensor
  • EGR valve and EGR hose
  • Ignition timing and system (advanced timing and ignition components are some of the most common problems)
  • Primary feedback sensor failure including, oxygen sensor, MAP/MAF, TPS, RPM, and CTS sensors
  • Vacuum lines
  • Catalytic converter

Diagnostics for HC failures

OVERALL

  • Check for cause of rich mixture, e.g. Oxygen Sensor
  • Check carburetor if equipped
  • Ignition timing and system (advanced timing and ignition components are some of the most common problems)
  • Check lines and hoses
  • Check catalytic converter

 

1981-86
Check the following:

  • Carburetor
  • O2 sensor
  • Ignition timing and system (advanced timing and ignition components are some of the most common problems)
  • Catalytic converter
  • Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
  • Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors

 

1987-95
Check the following:

  • Use OBD, if available
  • O2 sensor
  • Ignition timing (advanced timing and ignition components are some of the most common problems)
  • Catalytic converter
  • Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors.
  • Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)

 


Diagnostics for CO failures

 

OVERALL
Check for cause of rich mixture, e.g. Oxygen Sensor

  • Check carburetor if equipped
  • Check lines and hoses
  • Check catalytic converter

 

1981-86
Check the following:

  • Carburetor
  • O2 sensor
  • Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
  • Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors
  • Catalytic converter

 

1987-95
Check the following:

  • Use OBD, if available
  • O2 sensor
  • Fuel Injectors/Carburetors
  • Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors
  • Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)

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