WHAT’S INSIDE: Stratus Head Case...Pages 1&3 / FINE TUNING…Page 2 / HOT OFF THE WIRE: Airtex Vehicle Electronics Online...Page 4 / Publisher’s Information...Page 4

following locations:

The PCM relay control wire. Connectinghere tells me the PCM was commanding thesystem on. This pin provides the power to theair pump relay. This is the gold trace you'llsee in the capture in Figure 1 on page 3.

The MAF signal wire. Connecting here tellsme what the MAF was telling the PCM. Thisis the red trace in Figure 1.

The pump power wire, before the relay.Connecting a current probe here tells me thepump was running, and is the green trace inFigure 1.

This first screen capture (Figure 1) was takenwith the system connected as it should be.The gold trace shows the PCM is indeedsending the power to the relay, and thepump current pattern shows the relay isengaged and the pump is running. MAFincreased only slightly, however, to justunder 1.0 volt.

Could the MAF be reading incorrectly, or isit possible the correct reading wasn'treaching the ECM? Could it be a restrictionto airflow in the plumbing?

I disconnected the air tube at the one-wayvalve and tried again. Luckily, there wasenough "cold" engine to run the test onemore time. The pump didn't run as longthis time, but the increase in the MAF signalled me to believe the change was due to anair restriction.

I removed the one-way valve for a visualinspection. How did the valve get socorroded (Figure 2)? And why is the currentflow on the motor higher with therestriction removed? While there is nospecification, 34 amps had to be too much.The car was "new" to our customer, but Isuspect water had intruded into the pumpsomewhere in this car's past. I shared my

This diagnostic episode concerns a 2005Dodge Stratus with a 2.4L engine (vin J)and an automatic transmission. The MIL ison, and a DTC P0491 (air injection systemperformance) has been stored. The car onlyhas 39,000 miles on the odometer and isvery clean. After checking for applicableTSBs, and finding none, I pulled thetrouble code description to betterunderstand how the code was recorded.

The air injection system feeds extra air intothe exhaust when the engine is cold to morequickly heat the catalytic converter andbring it on line. This code is recorded whenthe PCM detects too little or too muchairflow through the system, and ismonitored with the engine running and theair injection pump commanded on.

A dedicated MAF sensor is located on theintake side of the air pump assembly toprovide feedback to the PCM, and it is thisfeedback that is a primary consideration in

the PCM's decision to turn on theMIL. DTC P0491 is a two-trip code.As a side note, this system does usefeedback from the oxygen sensor as

well, but this input only confirms a no-flow

hat’s wrongwith this picture? Itmay seem obvious now,but not so much withthe engine assembled.

continued on page 3

Stratus Head Case

condition and not a partial-flow fault.

Freeze frame information didn’t tell mewhich way the system had failed. This was ahard fault, and not an intermittent, becausethe "Good Trip" counter was still at "0."How best to proceed with my diagnosis?

I structure my diagnostic procedure tomimic what the PCM is doing as much aspossible. In the case of the P0491, the PCMcommands the air pump relay on, which inturn powers the air pump motor. Air ispulled through the filter, then the MAFsensor, before exiting the pump. From there,the air flows through a tube to a one-wayvalve located above the exhaust. This codeoccurs when the PCM knows it turned onthe pump and didn’t see the airflow itexpects to see – either high or low. Thepump only runs when the engine is cold,and for about 20 seconds or less.

The car was cold when I got it, which mademy choice of diagnostic approaches a littleeasier. I decided to hook up my scope to seethe system in actual operation. I could verifyall I wanted in a few screen shots. Usingthree channels, I connected the scope at the

WThis issue’s case study was contributed by Pete Meier.

T h e e l e c T r o n i c, d i a g n o s T i c a n d d r i v e a b i l i T y r e s o u r c e.

Volume 7 Issue 1, Summer 2012Counter Point

Tim HeidenTim’s Auto CareFreeport, IL

Gary LipschutzTires PlusPhiladelphia, PA

I am working on a 1997 Ford F150 with a4.2L engine. The engine runs great at idle.When accelerated to around 1000 RPMwhile power braking, cylinder number 5misfires. I have checked cylinder number 5and it never loses spark. I have changed thefuel injector and even moved the newinjector to a different cylinder and installeda known good injector into cylinder 5. Ihave also checked both cranking andrunning compression and it looked good.The vacuum gauge is steady so the engineappears to be mechanically sound. Whatcould be causing this misfire?

Steve Ayers Ayers Auto ElectricWrightsville, PA

If you have the answer, contact us at:E-mail: technical@airtexVE.comFax: (920) 922-3585Postal: CounterPoint Editor c/o Airtex Vehicle ElectronicsP.O. Box 70 Fond du Lac, WI 54936-0070

Follow Airtex Vehicle Electronics on:

In this space, we provide addresses of helpfulwebsites we’ve encountered during our travelson the internet. We hope you find these linksto be of value.

OBD-II Diagnostic Trouble Codes www.obd-codes.comIf you type “P0440” in a Google search, thisis the first site listed in the search results.This site provides DTC definitions, forums,as well as links to Airtex Vehicle Electronicsvideos.

Airtex Vehicle Electronics on YouTubewww.youtube.com/user/AirtextechThe videos found here are brought toyou through the efforts of the AirtexTechnical Services Department. It is ourgoal to bring you comprehensive automotivediagnostic and repair information you can putto use today.

Diagnose The Problem Win A ShirtDiagnose The Problem Win A ShirtRemember, he had spent more than a week offrustration prior to making that call. Wheredid we find the answer? On the internet, ofcourse, on a very helpful website run byIdentifix.

David was told to check for excessive ACvoltage from the alternator and guess what?The spec is no more than .5 AC volts and hewas reading nearly 8 AC volts. He replacedthe alternator and the problem was solved.

Let me close with this. Perhaps you find itdifficult to justify the time and money spenton learning. Perhaps you need to adjust yourthinking. What is a week’s worth of workworth to you?

Last issue’s Fine Tuning question concerned a2004 Ford Mustang 3.8L, VIN 4. The CheckEngine light (CEL) is on, and a DTC P0340(camshaft position sensor circuitmalfunction) has been stored in memory. Thecam sensor was replaced and the code cleared.However, the CEL popped back on during ashort test drive and the P0340 reset. Asecond cam sensor replacement yielded thesame result. The reader wondered if heneeded to install an OE sensor or ifsomething else could be wrong.

A: This cam sensor produces an AC wavesignal. This is the same type of signal, at adifferent frequency, that the alternatorgenerates, before the signal goes through thediode bridge and rectifier. If a diode in thealternator is failing, the vehicle’s charging andelectrical system will be subjected tounwanted AC voltage ripples. Theseunwanted signals can find their way into thecomputer system, either through the chargingsystem or through inductance. When thisoccurs, algorithm confusion can take place inthe on-board computer system, causing thecomputer to illuminate the CEL and store atrouble code. To verify this is the issue,disconnect the alternator, clear the code andgo on a short test drive. If the code does notreturn, the alternator is the cause.

Result: Jim disconnected the alternator andthe code did not return. He replaced thealternator and the problem was solved.

The first CounterPoint readers with the correctanswer to this diagnostic question were:

Q: I have been pulling my hair out for a weekwhile working on a 2006 Dodge Stratus witha 2.7L engine and about 60,000 miles on it. Itis setting a code P0720, but this is just asmall part of the problem. When the engine isidling but the vehicle is not moving, thespeedometer will jump and move as if thevehicle is moving down the road. The engineRPM will also increase along with thespeedometer movement.

I have replaced the transmission speedsensor, the transmission wiring harness, thePCM and have checked for TSBs. I have thefactory scan tool and have checked everycircuit thoroughly. Regardless of everything Ihave done, the problem persists. Can youhelp?

David Jameson Jameson RepairDenver, CO

A: Please keep this thought in mind if youare diagnosing an issue like this and all youend up doing is hitting brick walls. The yearis 2012; the computer and the age ofcommunication are here to stay. You shouldhave two tools at your fingertips that youknow how to use. These tools are acomputer with an internet connection and atelephone. If you haven’t considered thesetools by now, you need to step up and pullyourself out of denial.

There are many no-cost telephone calls youcan make to manufacturer helplines. Thereason they are there is to help you throughjust about any problem. Make a list of thesephone numbers, keep it by the phone, andmost importantly, use it.

If you have trouble working your wayaround a computer, ask someone for help.Your children or grandchildren are probablymore than willing to help you get started.You learn how to use a computer by using it,and yes, at times this means makingmistakes. But you are not going to kill thecomputer, so stop making excuses. There is awonderful informative world out there andyou need to be a part of it. It needs you tobe a part of it!

Within five minutes of the call David madeto our tech line, his question was answered.

Fine Tuning questions are answered byMark Hicks, Technical Services Manager. Please send your questions to: Mark Hicks c⁄ o Airtex Vehicle Electronics, P.O. Box 70, Fond du Lac, WI 54936-0070 or e-mail him attechnical@airtexVE.com. We’ll send you a very nice Airtex golf shirtif your question is published. So pleaseinclude your shirt size with your question.

2

My Hot LinksMy Hot Links

TuningFineFine

I should have removed the valve with theline the first time around to confirm thefault, but let the vehicle’s low mileage cloudmy judgment. I don't feel too bad. At leastI didn't install the wrong cylinder head.

Finishing this job took some doing. Thereisn't much demand for new cylinder headsfor the California version of the 2.4Lengine. Our dealer originally ordered areman head for us but when it arrived itwas a Federal-style head, just like the one Iwanted to replace. The final solution was toorder a brand new bare head casting andswap everything over.

As you can see, the Federal head has no portsfor the secondary air injection system (Figure4), while the California head does (Figure 5).The Federal head does, however, have an EGRport that the California head does not. Onthis job, the previous tech had tried to threadthe port and install a bolt to seal the hole.

As a last step, I hooked up my scope toverify the repair (Figure 6). I only watchedthe motor current and MAF signal, since I’dalready confirmed that the system wasworking. I wanted to know what a normalsystem would look like with no restrictionsin case I ran into something like this again.Hope you enjoyed the tale!

From the pump, the air flows through anylon line up to the rear of the cylinderhead to a one-way valve located on theexhaust manifold. This is where I originallythought the restriction was occurring, but Iwas wrong.

This time, I removed the valve with the lineattached and ran the engine again. Airflowed just fine. This is how I learned thateven though the valve was very hard toblow through, the spring pressure wasnormal and the pump was more thancapable of opening the valve. Therestriction had to be on the exhaust side,and that meant removing the manifold.

After passing the one-way valve, the airenters a separate chamber cast into thecylinder head. From there, individual portsare drilled into each exhaust port. This issimilar to the individual EGR ports youwould find on the intake side of someengines. These ports should not be clogged,considering the engine only had 39,000miles on it. But all the evidence indicatedthey were.

The ports were not clogged, because therewere no ports to clog! Somewhere in thiscar's past, the cylinder head had beenreplaced with a Federal emissions head, andthe ports were never drilled through. Thetech who did the work was smart enough toknow this wouldn't work, and doublegasketed the exhaust manifold after cuttingpassages of his own in the gasketsthemselves (Figure 4).

concerns with my boss, and sheauthorized replacement of the airpump and one-way valve.

Phase Two The one-way valve was replaced, along withthe air pump (there was a severe currentfluctuation in the original) and relay (asrecommended by the manufacturer whenthe air pump is replaced). The screencapture in Figure 3 in the next column wastaken after this repair.

This time, I added a channel to includebattery voltage. This allowed me toidentify the point on the capturewhen the key was turned on, theengine started, and then shut offagain. The information shows all is

working as it is supposed to, but still only0.10 volt change in MAF with the pumprunning. It looks like there is still arestriction somewhere.

The air pump on this system is controlledby a relay, which in turn is powered by theECM. The scope capture confirms that theECM’s command is being carried out. Airis drawn in through a filter located just

below the intake manifold, thenthrough a dedicated MAF sensor tothe pump.

Disconnecting the line at the one-way valvecaused the MAF voltage to increase to 5.0volts, which confirmed the MAF signal.

3

continued from page 1

Stratus Head Case

Figure 1: The gold trace indicates the PCM is sendingpower to the relay. The pump current pattern indicatesthe relay is engaged and the pump is running. MAFincreased only slightly, to under 1.0 volt.

Figure 3: The magnetic reluctance CKP is produc-ing a sine wave AC voltage pattern, but noise in thesignal may indicate a problem with the sensor.

Figure 4: There were no air injection ports to clog.Double gaskets were used during a previous repair,with slots cut out where the ports should have been.

Figure 5: This photo of the California-spec cylinderhead clearly shows the needed air injection ports. Oneof these heads isn’t that easy to come by.

Figure 6: Running a scope test after completing thehead replacement allowed me to verify the repair andalso provide known-good patterns for future reference.

Figure 2: How did this valve get so corroded? Andwhy is the current flow on the motor higher with therestriction removed?

This case study was provided by PeteMeier, Technical Editor of Motor Agemagazine. CounterPoint looks forwardto continued contributions from Pete,as well as other driveability instructors.Thanks, Pete for this great case study.

The AirtexVE YouTubechannel features 40different diagnosis andrepair videos, with newvideos added on aregular basis. Recentlyadded videos includeDIS Ignition Misfire,Ford DPFE Sensors,Digital EGR Valvesand Cam Sensors.

All videos are produced, filmed edited andperformed by technicians in the Airtex VehicleElectronics technical services department. Thevideos are relatively short. Each one documentsa real-world case study or explains how AirtexVehicle Electronics components have beenimproved to address a known problem with theOE part.

Wells President ..................David PeaceV.P. Sales & Marketing.......Bill NonnamakerTechnical Services Manager .... Mark HicksNewsletter Editor ................Karl SeyfertCounterPoint is a quarterly publication of AirtexVehicle Electronics, P.O. Box 70, Fond du Lac, WI54936-0070. Letters and comments should bedirected to: CounterPoint Editor, c/o Airtex Vehicle Electronics, P.O. Box 70,Fond du Lac, WI 54936-0070.

© COPYRIGHT 2012 AIRTEX VEHICLE ELECTRONICSAll rights reserved. No reproduction in whole or part is permittedwithout the written consent of Airtex Vehicle Electronics

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