DTC P0420 Catalyst System Efficiency Below Threshold (Bank1)

What, exactly, does this code mean? Is your catalytic converter at the end of it’s service life? The short answer here is Yes. Your converter is likely to be at fault for this code. Your vehicles On Board Diagnostics (OBDII) system monitors the upstream and downstream Oxygen Sensor readings and compares the switching of a rich-lean condition between the two.

The “upstream” O2 sensor, located in the exhaust stream before the converter, monitors the amount of oxygen in the exhaust gas as it leaves the engine while the “downstream” O2 sensor, usually located behind the cat or even in it, monitors the amount of oxygen in the exhaust gas after it passes through the converter.

When you first start your vehicle and the engine is cold, the upstream O2 sensor as well as the downstream O2 sensor will likely have about the same readings, as the gasses are not yet hot enough. Typically, the upstream O2 sensor changes from rich to lean very often as the engine computer adjusts the air/fuel mixture. However, when your vehicle reaches operating temperature, the exhaust gasses passing through the converter are hot enough to begin reacting with the metals inside of the converter ( platinum, rhodium and/or palladium – in some newer converters, GOLD! – Gold could actually increase oxidation, reducing pollutants even more!) and the downstream O2 sensor stays more so on the lean side.

Of course, that’s during normal operation. When the vehicle is at operating temperature and the downstream O2 sensor’s switching activity doesn’t tone down as per usual, that’s essentially telling the OBDII system that there is not enough oxygen coming out of the “cat”, so the converter isn’t properly oxidizing the hydrocarbons passing through it, the system sets a P0420 code and commands your malfunction indicator lamp on.

From here, you have few options if you want your Check engine light to go out – Replacement of your catalytic converter is looking more like the solution. In order to properly diagnose this issue, it is recommended that you bring your vehicle into a shop and mention to them your P0420 trouble code, allow that shop to do some trouble shooting and determine the cause and the fix.

However, for the DIY crowd, there are a couple of things you can check for before determining which action to take. Check for failure of the heated oxygen sensor(s) as well as an exhaust leak. If a faulty O2 Sensor is found, replace it. If you find an exhaust leak, repair it. Another possible cause of this code is a faulty PCM (Powertrain control Module). It can be difficult, if not complex, to test for these issues and a repair facility is recommended if you do not have the proper tools/instruments at hand.

C0265: EBCM Relay Circuit (open circuit)

After doing a bit of research on this code, i’ve learned that this code is referring to a non-serviceable relay located within the EBCM (Electronic Brake Control Module) itself. However, there are several things that can (and should!) be done first, before anybody replaces anything! Let’s take a look at at the issue.

Circuit Description
The EBCM internal relay supplies battery voltage to all six valve solenoids and the pump motor. The low side of each solenoid coil has a feedback circuit to the EBCM microprocessor. When the relay is commanded off, feedback voltage is low. When the EBCM relay is commanded on, feedback voltage is high.

Conditions for Setting the DTC
C0265
The EBCM microprocessor detects low feedback voltage from all of the valve solenoids when the relay is commanded on.

When the DTC is set, this action is taken:

• The ABS & BRAKE light indicators are commanded “on”.
• The ABS is disabled for the remainder of the ignition cycle.
• The EBCM aborts all other self-tests for components that are powered by the relay

DIY – Action you can take on, yourself

One of the first things I would do, is take the cover off of the Power Distribution Box under the hood. Check the owners manual or service manual for this vehicle & inspect any and all fuses that may have anything to do with the brake system. (While you’re under there, may as well check for any other bad fuses as well!

The next thing I would try, as per the research i’ve done, requires some tools and a little bit of patience. You may need a drill with a wire brush attachment as well as a ratchet & appropriately sized socket. I’ve read that some EBCM’s are unnecessarily being replaced due to a faulty ground, and at around $800.00 a pop, that’s too much money to “waste” unnecessarily.

Under the vehicle, in the frame rail directly below the drivers door is a ground cable. Possibly a few ground cables. If there are several, the one we’re looking for here is the thicker wire, probably a 12 guage wire. Remove it from the frame and clean the frame up nice with the drill & attachment. You’ll also want to clean up the ground strap where it attatches at the frame.

Once you’re done there, re-attach the ground to the frame & start your vehicle. If a faulty ground here is to blame, your troubles should be over and the lights will go out. If not, you may want to use your OBDII scanner (we all have one, don’t we?) to clear the trouble code. Test drive the vehicle to ensure the lights remain out.

If not, there is one other option you can try before you’re faced with a expensive bill. It’s been noted that a faulty battery to frame ground can also cause symptoms similiar to the above mentioned. Follow the negative battery cable from the battery to the ground on the frame. Perfrom the same cleaning steps above. If this doesn’t solve the problem, then the issue is highly likely due to the EBCM itself or the wiring leading to it. That’s a little more complex than the average DIY’er should undertake.

If the EBCM is deemed faulty and a replacement is necessary, just know it’s an expensive operation. The cost is probably around $800 or so for the part as well as an hour to an hour and a half’s labor time, plus programming charges, if necessary. This is exactly why you should perform the above steps first, hopefully you can save yourself a small fortune in these hard economic times!

That aside, we very recently had a 1999 Ford Ranger 4×4 Super Cab roll through our shop with an ABS light on. Almost immediately, I imagined it would be the speed sensor on the top of the rear axle as this is a common issue. After scanning her with the Genisys – we were given this code:

C1230: Speed Wheel Sensor Rear Center Input Circuit Failure

Turned out the initial suspicion of the rear speed sensor was correct. I replaced it with an aftermarket sensor from Advanced Parts which took all of 5 minutes and this took care of the problem. I cleared the code from the system and took her out for a spin. The ABS light has been out since.

I just wanted to share this bit of info as it’s a very common issue with these trucks, it isn’t very hard to repair at all and it’s pretty inexpensive. A job like this could be easily completed by a beginner DIY mechanic!

This is one of the more common questions that I am asked on a relatively regular basis. To understand the answer, it is important to understand the requirements under the hood. Within your vehicles engine, there are many metal surfaces that rotate, pivot or otherwise move very close to one another at high speeds. The primary goals of your engine oil are to keep those surfaces lubricated and cooled.

During engine operation, the engine oil is pushed through the engine oil filter in an effort to keep the oil free of contaminants. The filtered engine oil is then used to coat and lubricate moving parts, absorbing heat and washing away chemicals and other build-ups. The engine oil is then recycled through the engine oil filter, where the impurities are trapped, keeping them from cycling back through the engines crucial parts, minimizing premature parts wear.

The stress put on the oil in your engine is very hard to imagine. It is subjected to an immense amount of heat and pressure, it cleans an engines internals of chemicals such as silicon oxide along with other by-products and eventually, the stress becomes too much and the oil begins to break down on a molecular level. By this time, the engine oil filter is clogged and at the end of its usefulness.

Ideally, it is recommended to have your engine oil changed every 3 months, or every 3,000 miles. The idea behind that recommendation is to replace the engine oil filter before it is clogged and to replace the engine oil before it can no longer protect your engine to the best of its ability.

So, back to the question at hand, why do I need an engine oil & filter change? An engine oil & filter change is an inexpensive and quick operation and is widely considered as the most important preventative maintenance that can be done to your vehicle.

If a code is present, you have a decent starting point. For instance, a P0446 would indicate a blocked vent solenoid. Begin by inspecting this particular part. However, if no code is present, begin by visually inspecting the EVAP system by looking for cracked, broken or even missing vapor hoses which could cause vacuum leaks and the smell of fuel. Ensure that all hoses are routed correctly and connections at the tank, canister and engine are secure.

Inspect the fuel cap and fuel tank filler neck for damage and correct fit. On vehicles that have OBDII, something as simple as a fuel cap that is improperly installed can set a DTC causing a check engine light. That’s something to chew on for a while!

Inspect the canister for cracks or other damage. It’s important to inspect the canister air filter to ensure it’s not plugged up. If fresh air can’t be drawn into the canister, the fuel vapors can not be purged. On some EVAP systems, the air filter is actually replaceable. However, on most (that i’ve seen anyway) the whole canister must be replaced.

To check the EVAP system and ensure it’s working properly, connect a scan tool to the Data Link Connector (DLC). Start the engine and let it sit at idle. Using the scan tool, determine whether the solenoid is on or off. At idle, the purge solenoid should be off. Leave the scan tool connected and drive the vehicle. When the engine operating conditions for purging occur, again check the scan tool for purge solenoid operation. The solenoid should be on.

If the solenoid is off, check the power supply to the solenoid and the solenoid itself. PUrge solenoid valves can be tested to see if they will pass or block vacuum using a remote source of voltage and a hand vacuum pump. However, you must first determine whether the solenoid is normally closed or normally open. A normally open solenoid allows vacuum flow when de-energized. A normally closed solenoid blocks vacuum until it is activated by the PCM.

A thorough understanding of what is written here, can ensure that when you run into a EVAP issue, you can maintain a cool mind in a frustrating situation as well as be on top of your engine performance! Good luck!

The EVAP system is designed to “capture” these vapors and burn them off in the air/fuel mixture during combustion. Every EVAP system has the same components.

• Pressure/Vacuum Relief Fuel Cap
• Vapor Valve
• Charcoal Canister
• Canister Purge Valve

Not to mention the necessary plumbing connecting the Charcoal Canister to the Fuel Tank and the Charcoal Canister and the Engine Intake. The fuel tank cap has a pressure and vacuum relief valve. The vacuum valve allows air into the fuel tank to replace the fuel as it is used, all the while preventing fuel vapors from leaving the fuel tank. The vapor valve is usually found on the fuel tank or near it and lets fuel vapor (but not liquid) to flow from the tank to the charcoal canister.

The charcoal canister contains activated charcoal that allows it to temporarily “hold” the fuel vapors from the fuel tank. The canister holds these vapors while the vehicle is not running. When the engine is running and under certain operating conditions, a valve between the canister and the engine opens to let fresh air into the canister’s air filter. This mixture of fresh air and fuel vapors are then drawn into the engine and burned. This is what is called “Purging”.

Where EVAP systems differ is the when and how canister purging takes place. Earlier systems ported vacuum and a check valve to make sure purging would not happen at idle and utilized thermovalves to ensure that purging only occurred after a certain operating temperature was reached. Emissions laws evolved, therefore Emissions systems had no other options but to evolve as well.

Modern EVAP systems are computerized (as most things are these days!). The charcoal canister is controlled by the Powertrain Control Module (PCM). The PCM determines when the canister should be purged based on various sensor readings. When purging is required, the PCM operates a solenoid valve that controls the vacuum to purge the canister.

In general, the purge solenoid is activated when the engine is running above idle speed and at least at operating temperature. Enhanced EVAP systems are equipped with a canister vent solenoid, which is found in the fresh air supply hose to the sealed charcoal canister. Non-Enhanced systems have open-atmosphere canisters. The canister vent solenoid is normally open, allowing fresh air to be drawn into the canister. The PCM controls the solenoid during the EVAP leak test to block the entrance of outside air.

Keep an eye out for a follow up article to this one: Evap Emissiosn: Diagnosis & Testing.

Let’s begin with some parts that we will need in order to perform a proper tune up on today’s vehicles.

• Air Filter
• Oil Filter
• Engine Oil (Correct Viscosity!)
• Spark Plugs
• Spark Plug Wires
• Distributor Cap
• Ignition Rotor
• Fuel Filter

Some vehicles are also equipped with an Air Cabin Filter. If your vehicle has one, it should be checked for moisture & whether or not it’s plugged, the Air Cabin Filter housing must be cleaned of any debris to help keep the vehicle inlet air clean.

Checking & Replacing Parts

Air Cabin Filter – If equipped, locate the Air Cabin Filter housing. It is usually under the dash on the passenger side or under the hood near the rear of the cowl. If moist, customer complaints may include odd odors in the vehicles cabin and the filter should be replaced and the housing needs to be cleaned. If plugged, customer complaints may include lack of air flow into the vehicles cabin and the filter should be replaced.

Air Filter – The air cleaner in your vehicle should be changed every 3,000 miles or sooner depending on driving conditions. If you’re often driving in dusty conditions, the air filter should be checked regularly and replaced or cleaned as necessary.

Oil & Filter – The engine oil & filter should be replaced at regular intervals of around 3 months, or 3000 miles. The idea behind that recommendation is to replace the engine oil filter before it is clogged and to replace the engine oil before it can no longer protect your engine to the best of its ability. Feel free to read the article linked here for a more in depth explanation.

Spark Plugs – A spark plug is used to ignite the fuel air mixture inside the combustion chamber. If a spark plug becomes worn or damaged it can cause poor performance and fuel economy and should be replaced at a manufacturers recommended mileage.

Spark Plug Wires – Each spark plug wire is connected to a spark plug, and brings the electrical spark to the spark plug in order to ignite the fuel inside the engine’s cylinders. A damaged spark plug wire can make your car run rough and affect gas mileage. Remember to replace spark plug wires ONE at a time so as not to cross wires! Keep in mind that not all ignition systems are set up the same but they operate on the same principle. Some vehicles have a Direct Ignition system consisting of a coil over the spark plug (COS) and spark plug wires are not required!

Distributor Cap & Rotor – The distributor cap and rotor are two essential pieces that distribute electrical current to the spark plugs. The distributor cap connects to the spark plugs directly using a spark plug wire. The rotor is designed to spin inside of the distributor cap, just missing the terminals inside the cap. A worn or damaged rotor can cause your vehicle to run rough, or even stall completely. The rotor is rotating at the same speed as the camshaft which also happens to be 1/2 the speed of the crankshaft.

A problem occurs when the contacts inside the distributor cap become dirty or worn. It is good practice to replace the distributor cap and rotor during every tune up to ensure the contacts are clean to transmit power to each spark plug.

Fuel Filter – A vehicles fuel filter is used to keep the fuel in the fuel system clean to prevent debris from entering the fuel injectors or fuel pressure regulator. The fuel filter should be replaced during every major tune up or every 25,000 miles.

Let’s move onto another aspect of a complete tune up.

Throttle Bore Service

Vehicles that have an air intake system should also undergo throttle bore service or inspection during any tune up. It is just good practice. The air intake boot should be removed from the throttle bore and the bore inspected. If there is any signs of coking (build up of carbon, dark but light tar residue), the throttle bore should be cleaned out. Rubbing alcohol works really well or a commercially available solvent can be purchased.

“Coking” can be the cause of a ‘sticky’ accelerator pedal, engine stalling, odd engine idle or even poor fuel mileage.

Remember, when a customer comes in and specifically requests a tune up, it is good practice to talk with the customer and find out if there are any driveability issues they are trying to resolve. It is possible that they have other issues that may not be repaired during the tune up and this will result in a poor customer relationship from the start.

A good attitude and good customer service skills are the most over-looked skills that makes a good technician, a great one.