scan tool

When the check engine light is turned on the computer is notifying the driver that one of the channels that it is monitoring is out of the specific range that is burned in memory. When this light comes on the car may have set a single code or multiple codes.

An example of why the check engine light comes on would be an oxygen sensor code. The range of operation that the computer is looking for is between 60 and 800 mV. In this specific example, the computer is also monitoring the changes in the voltage. If the oxygen sensor returns data that is out of this range, the check engine light is turned on to notify the driver of a car problem.

Does this mean that replacing the oxygen sensor would turn off the check engine light? The answer is in most cases is replacing the sensor will not turn off the light. The reason that the check engine light is on is because the sensor is out of range.

This may be because the sensor is faulty, but more than likely, the sensor is operating correctly and is out of range due to an air fuel mixture problem. Does this mean o2 sensors never go bad? Well they do but for the most part an oxygen sensor will last for about 125,000 miles or more. How do you fix it then?

What I do is pop into my online auto repair manual and look up the code. Then I perform a quick visual inspection to make sure no harm has come to the wiring like a mouse or damage from road debris ect... Next I follow the diagnostic flow chart for the specific code. Taking the same approach for each code set yields good results!

A little bit of history about the automotive scan tool. When I first got in the business in 1983 computer-controlled vehicles had just started to come around. The first scan tool I bought had replaceable cartridges. With every passing year, my auto scan tool would require a new cartridge.

The scanner was about $500 and each cartridge was about an additional hundred dollars. By the time 1987 rolled around, I couldn't even get cartridges for my auto scan tool. The reason being is that the vehicle communications systems advanced past the capabilities of my scan tool.

Thanks to the federal government in 1996, they decided that there should be a standardized method of communication and diagnosis for the emissions and computer-controlled systems on all vehicles. This standardized system is known as OBD 2. So what this means to the general automotive consumer is that there vehicle has the same diagnostic capabilities as a BMW, Mercedes-Benz, and foreign or domestic vehicle. They are all the same.

The fact that all of these vehicles are now standardized means that the scan tool has also been standardized and has allowed the price to fall dramatically for automotive scanners. I also put together a page about how to use a scan tool if you would like to review the easy operation of this tool.

If you buy an auto scan tool. You can rest assured that your new purchase can be used on any vehicle from 1996 through 2007 and beyond. On my main website, I provide information on common codes how to read scan tool data and auto scan tool reviews of three tools that I own in three different price ranges. My first scanner that I bought in 1983 is completely useless today.

I spent close to $1000 on something that only lasted about three years. Today you can take advantage of the new technology and buy an auto scan tool for less than $100 that will not only be good for the last decade of vehicles, but will also continue to work on the newer vehicles for the foreseeable future. Visit my reset check engine light procedure page for more details.

A separate computer and separate scan tool are needed for the proper diagnosis of the ABS system on most vehicles. When the ABS system turns on the warning light it will set a code just as in standard OBD 2 applications. These codes relate to a specific failure, in part of the computerized antilock braking system.

On modern four-wheel antilock brake systems the ABS computer monitors wheel speed through four independent wheel speed sensors and compares that to the vehicles Main speed sensor, which is usually located in the transmission output shaft area, but can also be located on the rear differential.

When the computer sees a difference between the actual speed of the vehicle and an independent wheel. It begins to pulse the brake system through a computer-controlled brake modulator.

Common causes of ABS lights.

If you have an ABS scan tool you can retrieve the code from the braking system computer that will point you directly to the malfunction area.

My experience with diagnosing this system is that the individual wheel speed sensors are fragile and are easy to damage.

Visit auto-facts.org for more information about common anti-lock brake problems and a review of the Actron abs scan tool pictured here.

I do not own a laptop computer or a PDA so I have resisted this technology. But recently the Government fleet repair center I work for decided to add one to the Panasonic Tough book we use in the shop.

Our tough book runs windows vista and already has a few programs on it for diagnosing and troubleshooting thermo king electronic a/c systems. We also use it for the computer controlled Allison transmissions in the fleets heavy duty units. So it seemed logical to add the OBD capabilities for our light duty fleet applications as well.

I installed it myself and scanned the first vehicle with the reasonably priced OBD II blue tooth version of the Elm Scan Five. See if this automotive scanner for laptops is right for you?

If you have set a code the best way to fix it is with a professional diagnostic chart for that specific code. All-Data pulls their information directly from the factory auto repair manuals.

A scan tool used in conjunction with this manual has been 100% effective for me. See the above link for a home made screen capture video I put together. The demonstration shows how this program works for all kinds of do it yourself auto repair.

Having your own auto scan tool can help you save money and time by avoiding an unneeded trip to the dealership or automotive repair center for diagnosis.

It is very common these days to have your service engine soon light just pop on. If you had your own auto scan tool, you would be able to retrieve and record the code and then clear the code to see if it was an intermittent problem. If the service engine soon light does not come back on.

You have just repaired your vehicle in a span of about 10 minutes. You have also just avoided a trip to the auto repair center, which is priceless. If the service engine soon light comes back on, you will be able to reconnect the auto scan tool and verify that the same code as been set.

You would then diagnose the code yourself using an online auto service manual such as All-Data online DIY car repair manuals.

Or you can even take the vehicle to your repair center, but with the information that the auto scan tool has provided for you. This can cut down on the shop's initial diagnosis. You have already cleared the codes and done the first major step of diagnosis for the auto repair center, this will save you money on diagnostic charges.

I own 4 scanners for reading codes and diagnosing check engine lights. I provide pictures and details about each one on my automotive scanners review page.

If you take your automotive scanner and use it in conjunction with a specific repair diagram for the individual code set in the computer you will have the quickest most reliable path to successfully repairing your check engine light.

The diagnostic charts from Mitchell have recently been made available online and for instant access. You can locate and print the exact diagram you need for the cheapest price ever offered!

I provide a demonstration video of how to use this program and get the most out of it. Visit my page about auto repair online and fix your own car!

Give this page a


This list is not every trouble code in existence! These are instead the more common and in my opinion likely to be found when performing a diagnostic scan.

P0016 Crankshaft/Camshaft Timing Misalignment
P0037 HO2S-12 (Bank 1 Sensor 2) Heater Relay Circuit Low Input
P0038 HO2S-12 (Bank 1 Sensor 2) Heater Relay Circuit High Input
P0051 HO2S-21 (Bank 2 Sensor 1) Heater Relay Circuit Low Input
P0052 HO2S-21 (Bank 2 Sensor 1) Heater Relay Circuit High Input
P0056 HO2S-21 (Bank 2 Sensor 1) Heater Relay Circuit Malfunction
P0057 HO2S-21 (Bank 2 Sensor 1) Heater Relay Circuit Low Input
P0058 HO2S-21 (Bank 2 Sensor 1) Heater Relay Circuit High Input
P0070 Battery Temperature Sensor Circuit Stuck
P0072 Battery Temperature Sensor Circuit Low Input
P0073 Battery Temperature Sensor Circuit High Input
P0107 Manifold Absolute Pressure Sensor Low Input
P0108 Manifold Absolute Pressure Sensor High Input
P0111 Intake Air Temperature Sensor Range/Performance
P0112 Intake Air Temperature Circuit Low Input
P0113 Intake Air Temperature Sensor Circuit High Input
P0117 Engine Coolant Temperature Sensor Circuit Low Input
P0118 Engine Coolant Temperature Sensor Circuit High Input
P0121 Throttle Position Sensor Does Not Agree With MAP
P0122 Throttle Position Sensor Circuit Low Input
P0123 Throttle Position Sensor Circuit High Input
P0125 Closed Loop Temperature Not Reached
P0129 Barometric Pressure Sensor Out-Of-Range Low
P0131 HO2S-11 (Bank 1 Sensor 1) Signal Low Input
P0132 HO2S-11 (Bank 1 Sensor 1) Signal Shorted to Voltage
P0133 HO2S-11 (Bank 1 Sensor 1) Slow Response
P0135 HO2S-11 (Bank 1 Sensor 1) Heater Circuit Malfunction
P0136 HO2S-12 (Bank 1 Sensor 2) Heater Relay Circuit Low Input
P0137 HO2S-12 (Bank 1 Sensor 2) Signal Low Input
P0138 HO2S-12 (Bank 1 Sensor 2) Signal Shorted to Voltage
P0141 HO2S-12 (Bank 1 Sensor 2) Heater Circuit Malfunction
P0165 Starter Relay Circuit Malfunction
P0171 Fuel System Lean (Bank 1)
P0172 Fuel System Rich (Bank 1)
P0174 Fuel System Lean (Bank 2)
P0175 Fuel System Rich (Bank 2)
P0201 Fuel Injector 1 Control Circuit Malfunction
P0202 Fuel Injector 2 Control Circuit Malfunction
P0203 Fuel Injector 3 Control Circuit Malfunction
P0204 Fuel Injector 4 Control Circuit Malfunction
P0205 Fuel Injector 5 Control Circuit Malfunction
P0206 Fuel Injector 6 Control Circuit Malfunction
P0207 Fuel Injector 7 Control Circuit Malfunction
P0208 Fuel Injector 8 Control Circuit Malfunction
P0300 Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0307 Cylinder 7 Misfire Detected
P0308 Cylinder 8 Misfire Detected
P0315 Crankshaft Position Sensor Not Learned
P0320 No Crank Reference Signal to PCM
P0339 Crankshaft Position Sensor Circuit Malfunction
P0340 No Camshaft Signals At PCM
P0344 Camshaft Position Sensor Circuit Intermittent
P0351 Ignition Coil 1 Primary Circuit Malfunction
P0420 Catalyst Efficiency Below Normal (Bank 1)
P0432 Catalyst Efficiency Below Normal (Bank 2)
P0441 EVAP Purge Flow Monitor Fault
P0442 EVAP System Small Leak (0.040") Detected
P0443 EVAP Purge Solenoid Circuit Malfunction
P0455 EVAP System Large Leak (0.080") Detected
P0456 EVAP Leak Monitor Leak (0.020") Detected
P0460 Fuel Level Sensing Unit No Change Over Miles
P0461 Fuel Level Sensing Unit No Change Over Miles
P0462 Fuel Level Sensing Unit Volts Too Low
P0463 Fuel Level Sensing Unit Volts Too High
P0500 Vehicle Speed Sensor Signal Circuit Malfunction
P0505 Idle Air Control Motor Circuit Malfunction
P0522 Engine Oil Pressure Sensor Circuit Low Input
P0523 Engine Oil Pressure Sensor Circuit High Input
P0600 PCM Internal Failure, No SPI Communications
P0601 PCM Random Access Memory Failure, Self-Test Failed
P0700 Automatic Transmission System Malfunction Detected
P0705 A/T Check Shifter Signal Circuit Malfunction
P0711 A/T Transmission Fluid Temperature Sensor Signal - No Rise After Startup
P0712 A/T Transmission Fluid Temperature Sensor Low Input
P0713 A/T Transmission Fluid Temperature Sensor High Input
P0720 A/T Output Speed Sensor - Low Output Above 15 MPH
P0740 A/T Torque Converter Clutch - No RPM Drop at Lockup
P0743 A/T Transmission Relay Circuit Malfunction
P0748 A/T Governor Pressure Solenoid/Transmission Relay Fault
P0751 A/T Overdrive Switch Pressed Low For Over 5 Minutes
P0753 A/T 3-4 Solenoid/Transmission Relay Circuit Malfunction
P1195 HO2S-11 (Bank 1 Sensor 1) Signal Insufficient Activity
P1196 HO2S-21 (Bank 2 Sensor 1) Signal Insufficient Activity
P1281 Engine Is Cold Too Long
P1282 Fuel Pump Relay Control Circuit Malfunction
P1294 Target Idle Speed Not Reached
P1296 5-Volt VREF Supply Not Present
P1297 No Change In MAP Signal From Start To Run Transition
P1299 Vacuum Leak Present With IAC Valve Fully Seated
P1388 ASD Relay Control Circuit Malfunction
P1389 No ASD Relay Voltage At PCM
P1391 CKP or CMP Sensor Signal Malfunction (Intermittent)
P1398 Misfire Adaptive Numerator At Limit
P1486 EVAP Leak Detection Monitor Pinched Hose Detected
P1491 Radiator Fan Control Relay Circuit Malfunction
P1494 EVAP Leak Detection Pump Switch Or Mechanical Fault
P1495 No CCD Messages Received From The BCM
P1740 A/T TCC or Overdrive Solenoid PSI In Gear At 0 MPH
P1756 A/T Governor Pressure Not Equal To Target At 15-20 PSI
P1757 A/T Governor Pressure Above 3 PSI In Gear At 0 MPH
P1762 A/T Governor Pressure Sensor Offset Volts Too High/Low
P1763 A/T Governor Pressure Sensor Signal Too High
P1764 A/T Governor Pressure Sensor Signal Too Low
P1765 A/T Switched Battery Malfunction
P1899 A/T Park Neutral Switch Stuck in Park Position or In Gear

Now you know what the code means. Next step is to figure out what made the
check engine light code set in the first place!