For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2012 Rick Muscoplat

One of the common air leaks is in the rubber hose

PCV valve elbow

going to the PCV valve. The hose has a 90 degree bend in it and it tends to crack there. So START your diagnosis by replacing both the PCV AND the hose. Many readers report that Ford doesn’t stop this hose. If you can’t find it, check the link below. Since this part has such a huge failure rate, Dorman has stepped into the market with a replacement. Install the elbow, clear the code and then see if it returns.

Want more more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!

© 2011 Rick Muscoplat

Here’s a typical example:

P0137 – Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)

Now most of you would say the computer has determined that the oxygen sensor is bad. That’s NOT what the code says. It merely says the circuit voltage is low. Low voltage on an oxygen sensor is almost ALWAYS caused by a vacuum leak. Why? Because as air gets into the system, the air/fuel mixture is too lean. A lean mixture produces a low voltage on the oxygen sensor. Replace this oxygen sensor without fixing the vacuum leak and you’ll get the exact same code again. Only this time, you’ll be out $80 for a sensor.

How can you tell if you should replace the sensor? Get a REAL scan tool. Then learn how to interpret short term and long term fuel trims. It’s actually very easy. Read this article on scan tools.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!

© 2011 Rick Muscoplat

Catalytic Converter

just because they’re seeing these codes. Perhaps not. But before I dig into what may be causing the problem, let’s do a quick explanation of exactly what a catalytic converter does and how it may fail.

Inside the catalytic converter you’ll find a honeycomb coated with rare-earth metals like Rhodium, cerium, platinum, and palladium. These metals react with oxygen, fuel, oil, to reduce the amount of carbon dioxide and oxides of nitrogen released into the atmosphere.

To check on the efficiency of the catalytic converter, manufacturers install an oxygen sensor in front of and behind the converter. The front oxygen sensor is very busy. It constantly senses changes in the exhaust. In fact, a properly operating oxygen sensor senses switches from lean to rich mixtures as often as 10-times per second. That data gets fed back to the computer to alter air/fuel mixtures going into the engine. If the catalyst is operating properly the post-cat sensor should see VERY FEW changes.

Now let’s talk about how it all works.

Hot exhaust gas warms the metals in the cat converter to about 475-575 degrees F. At that point the cat converter is referred to as “lit up.” In other words, that’s hot enough for it to start doing it’s job of burning off excess fuel and oil. As soon as the cat converter see excess fuel, the catalytic operation begins and the operating temperature rises to 1,200- 1,500 degrees F. The converter can easily handle those temps. But if the engine is misfiring and dumping excess fuel or the engine is worn and dumping excess oil, the converter can overheat to upwards of 2,500 degrees. At that point the ceramic honeycomb begins to melt and self destruct. Please re-read the previous sentence. The point is cat converters self destruct BECAUSE of engine misfires and worn engine conditions that dump too much fuel and oil. They don not fail from normal use.

There are a few other things that can kill a cat converter. First, if you think your car is a real screaming machine and you’re dumb enough to run racing oil in it, the extra friction modifiers in racing oil (zinc and phosphorous) will kill the converter. If you do an engine repair and use too much RTV sealant or the sealant isn’t “sensor safe” that too can kill a cat converter. Finally, a coolant leak can foul oxygen sensors. At that point they’re blind and with no fuel control, you’ve set up the conditions for converter burn out.

Now let’s focus on the codes

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
P0422 Main Catalyst Efficiency Below Threshold (Bank 1)
P0423 Heated Catalyst Efficiency Below Threshold (Bank 1)
P0424 Heated Catalyst Temperature Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)
P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)
P0432 Main Catalyst Efficiency Below Threshold (Bank 2)
P0433 Heated Catalyst Efficiency Below Threshold (Bank 2)
P0434 Heated Catalyst Temperature Below Threshold (Bank 2

Every control module runs a catalyst efficiency “monitor.” In other words, it runs a cat converter test. First, it determines that the engine is up to operating temperature. To do that it looks at the engine coolant temp sensor. Next, it looks at the upstream oxygens sensors to

Oxygen Sensor

ensure they’re switching from lean to rich (or vice versa) at least 10-times per second. If the upstream sensor is working and the cat converter is working, then the downstream sensors (after the car) should be seeing any variations. That would mean the cat converter is doing it’s job of converting fuel, oil, carbon dioxide, and oxides of nitrogen into harmless compounds. To sum up, the computer is looking for a rapidly changing upstream sensor and a very quiet downstream sensor. If the downstream sensor is active and exceeds the standards by 1.5 times, the computer determines that the catalyst efficiency is below threshold. It then sets a P0420 trouble code. The big mistake DIYers make in not checking other codes.

For example, if the upstream O2 sensor is failing (called a lazy sensor
because it’s not switching often enough) the computer may be dumping too much fuel into the mixture. That extra fuel may cause the POST O2 sensor to vary too much. That’ll set a cat converter code and trick you into thinking the converter is bad. So first address any OTHER codes present before you even think of swapping out the cat converter.

To check for a lazy sensor (one that’s failing enough to cause a problem but not serious enough to set a trouble code) most technicians use a scope. But you can use a scan tool –one that includes a readout for “cross counts” (that’s the technical term of when an oxygen sensor switches from lean to rich and vice versa). You should also check Short and Long Term Fuel Trim. If those numbers are 0-10%, you’re ok. But if they’re between 11-25%, the computer is adding too much fuel and that’s an indication of a serious problem. You can see how important it is to own a serious scan tool if you really want to diagnose the root cause of the problem. Buy one here.

Live Data Scan Tool

However, if you don’t own a scan tool and want to solve the problem yourself, start by replacing the UPSTREAM O2 sensors. That may sound counterintuitive since the codes actually indicate a problem with the downstream sensors. But remember, it the UPSTREAM sensors that control air/fuel mixtures. If they’re going bad, the air/fuel mixture will be screwed up and that will interfere with the downstream sensor readings.

If you’ve replaced both upstream sensors and the code still persist, then it’s time to replace the downstream sensors. Still have a code? Well, now you’ve got one more option. Force the cat converter into “clean out” mode. This involves dumping so much extra fuel into the exhaust that it forces the cat converter to overheat and possibly burn off the contamination. Yes, this procedure and also destroy the converter—but you’re already at that point and don’t have much more to lose. To perform this procedure, disconnect a spark plug wire or coil pack wire and run the engine at 1,500 to 2,000 RPM for about 5-10 mins. The extra fuel from the misfiring cylinder should raise cat converter temps to almost 2,000 degrees. After 10 minutes, reconnect the spark plug or coil pack wire and take it for a hard drive at freeway speeds. That should force enough of the burned off carbon buildup out of the converter. If it works, you just saved yourself $1,200. If it doesn’t, you lost nothing but some extra gas.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

This codes sets if the fuel pump is not starting up properly. Two things can interfere with fuel pump startup—the fuel pump relay or the inertia switch. Start by checking the fuel pump fuse. Next, manually reset the intertia switch. If that doesn’t work, check for power at the fuel pump connector. If you’re not getting power, pull the fuel pump relay (or swap it with another relay with the same part number) or jumper the relay contacts to power the pump. If that still doesn’t work, check for power coming into the relay. If you have good power, re-jumper the relay contacts and check for power coming out of the fuse box and going to the fuel pump. If you’re still fighting a losing battle, check the wiring crimp connectors. Some techs report faulty factory crimps at the relay box.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

If you think you should replace the knock sensor after getting this code, think again. This is a perfect example of where a sensor can be telling the truth and the root cause of the problem is somewhere else. Here’s the scoop. Most late model engine use variable valve timing to change the opening and closing timing of the valves. The device that actually changes the valve timing is called the cam phaser (yeah, like on Star Treck). Some cam phasers use oil pressure to rotate the camshaft slightly to change the timing. That’s great when it’s working well. But if you’ve changed your own oil and used a viscosity that’s different from the manufacturer’s recommendations, you can screw up the phaser. For example, some people don’t believe the manufacturer’s recommendation to use 5W-30. So they change their oil with 10W-30. The slightly thicker oil can cause the phaser to respond more slowly to computer commands. And when the cam is out of phase from the commanded position, you can get pre-ignition, or pinging. Yup, if you used this oil and now have this trouble code, point your finger right at yourself.

The same holds true if you think you can get away with not changing your oil on time. Think sludge buildup isn’t a problem? Well guess what, sludge in a cam phaser can also cause trouble codes.

If you’re getting these codes and think it might be caused by oil, change your oil and filter and drive the vehicle first. Perhaps the clean oil can clear out the passages.

Here are a few other things that can cause this trouble code:

Check the electrical connector on the cam phaser. If you see oily buildup, disconnect the connector and check inside. Oil can sometimes seep into the connector and that would give false readings.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Today, I hear DIYers whine every time their check engine light goes off and they have to get the codes scanned. My take on this is “GROW UP!!” If you want to do your own car repairs, you need a basic set of tools. And today, that means you have to own either a code reader or a scan tool. Don’t want to make the investment? Fine, then take it to a shop and pay them $100 a pop to hook up their scan tool.

Have I convinced you to buy your own scan tool yet? If so, let’s take a look at the offerings. Rather than review tools from every manufacturer, I’ll give you my bias right up front. SPX is a major tool manufacturer. They’ve been making specialty tools for most (GM and FORD all specify SPX’s tools) car makers for decades. When electronics came into play, Owatonna Tool Company (OTC) was the first to build scan tools for independent shops. OTC is owned by SPX. Next, SPX bought Actron, which used to be known as KalEquip (they made my tach/dwell meter back in the ‘60’s). They also bought AutoXRay. What I’m getting at is that SPX not only has direct connections to the car makers, but they own the top scan tool companies in the world. That’s why I tell readers to buy their tools.

What’s the difference between a code reader and a scan tool?

A code reader just reads the trouble code. That’s it. They’re cheap (less than $50), but they don’t do much for you. Once you get the code, you’re one step closer to solving the problem, but you’re still missing a LOT of critical information. If you’re a real cheapskate and only want to buy a code reader, here’s what to look for.

The cheapest code readers don’t have batteries. That means you can scan for the code and read the trouble code only as long as it’s plugged into the computer. Once you have the code, you’ll have to go to your home computer to look up the code definition. What a pain. But then again, you are a cheapskate. Oh, by the way, once you unplug it, the information is gone. So you’d better bring a pen and paper with you. But if you spend a bit more, the code reader will have a battery that maintains the code information in memory. Dig a little deeper and you’ll get a code reader with a back-lit screen. Dig deeper still and you’ll get a code reader that’ll spit out the code definitions right on the screen. And many of those higher end readers are update-able (as manufacturers develop new codes).

Or, get a real diagnostic tool

Let’s not kid each other—a code reader is a toy. Sure, it’ll give you the code, but that’s it. If you’re like most DIY’ers, you’ll get the code definition and replace every part mentioned in the trouble code. So if the code says oxygen sensor lean, you’ll replace the oxygen sensor. The parts manufacturer’s love people like you. Every year tens of thousands of perfectly good 02 sensors are replaced just because the trouble code contained the words oxygen sensor. Engine computers are smart, but they’re not that smart. They may tell you that the oxygen sensor is reporting a lean condition. You assume that means the sensor is bad. Most often it’s telling the truth, the exhaust stream really IS lean. What would cause that? Yup, a vacuum leak. But you won’t get to that point until you’re replaced an $80 sensor and wind up with another check engine light. How to get around that? Buy a scan tool that gives you live data and then learn how to interpret the data.

Here’s how live data helps you

When an engine computer sees a lean condition in the exhaust, the first thing it does is add more fuel to the mixture. This is called Fuel Trim. The computer tracks how much fuel it adds or subtracts. It can add or subtract up to 25%. So, if you’re seeing a lean or rich trouble code, the first thing you should do is look at the live fuel trim data. If the computer is adding fuel, that’s an indication of a vacuum leak. If it’s subtracting fuel, that’s an indication of a leaking fuel injector or a fuel pressure problem. Do you see where this is going? A scan tool gives you the data to actually diagnose the problem. THAT’s why you should pony up the money and buy a scan tool with live data. Yes, they’re expensive. But trust me, you’ll waste far more than that by replacing perfectly good parts because you were too cheap to buy a real diagnostic tool in the first place. Let’s see, you replaced both O2 sensors ($160) and the check engine light is still on. And the root problem was caused by a .25 vacuum hose? You could have owned a scan tool for close to that same money.

Buying Tips

I’m listing many models of Actron and AutoXray tools here. Do not buy them based on price. Read their specs and MAKE SURE the one you like actually works with your vehicle. Many of the less expensive scan tools do NOT read manufacturer-specific codes–especially on European vehicles. You’ll have to spend upwards of $300-$500 to get that capability. Finally, none of these inexpensive tools will read ABS, AIRBAG, Chassis, or Universal codes. To get that capability, you’ll have to spend about $2,000. Want that? Great. Buy an OTC Genisys scan tool.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

© 2007 Rick Muscoplat

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.