Finding intermittent faults on Fords

What is Ford’s Pinpoint Test Z?

It’s a test that is designed, in my opinion, to do two things. First, it can teach you how vehicles work. It does this by grouping inputs and outputs that are related to each other and most likely will show a concern caused by certain problems. Second, it will help you learn the test procedures that Ford uses throughout their service manuals, specifically test drives while gathering data and the wiggle test.

In this image we see the expected PID values for the 2010 Flex at different operating conditions when the vehicle is at or near sea level. 

Pinpoint Test Z details which Parameter Identifiers (PIDs) a Ford Powertrain engineer would use if he or she had a vehicle that was exhibiting a specific concern. This is why I say that you can use it to help you learn how vehicles work.

There is one caveat to my discussion. What service information system are you using? If you use a source other than Ford’s PTS website, the path to Pinpoint Test Z may or may not be accessed easily. Sometimes, aftermarket service information systems repackage the factory information, and other times maintain a similar format to the original. Be diligent, it is in there somewhere.

In a previous article, I talked to you about how to find intermittent misfires in Ford’s using fuel trim and the downstream (post-catalytic converter) 0₂ sensors. Once you learn to use the procedure in Ford vehicles, you can apply the same procedure on most other manufacturers’ vehicles. The same applies to Pinpoint Test Z.

A quick review might be in order. In that article, I said that if you had an intermittent misfire caused by an ignition concern, the downstream 0₂ sensors would go to high-voltage, greater than 600 mV. Fuel trims (FT) would increase by less than 20 percent and in many cases less than 10 to 15 percent from the non-misfire baseline.

This image shows the BARO PID values for different altitudes. When watching these values on a scan tool it is not unusual for them to change by 1Hz, maybe 2Hz, from standing still idle. 

For example, if FT was +15 percent (a potential issue itself) without a misfire then it will increase to about 25 to 30 percent during the event. The heated oxygen sensor (HO2S) downstream will be over 600mV and often at 1.0V.

An intermittent misfire caused by a fuel concern typically would cause the fuel trims to increase by more than 20 percent and downstream 0₂ sensors to go low-voltage, less than 100 mV.

For example, a vehicle with a baseline of FT at -5 percent as it begins to misfire caused by a lack of fuel, FT will go beyond +15 percent. I have seen them actually increase by more than 30 percent during this type of misfire event. The downstream O₂ sensors will be at less than 100mV

Watching your scan tool while these events occur and comparing before and after will give you good direction on where to test next to find your concern. The question is how did I determine which PIDs to monitor to determine the cause? The answer can be found in Ford's Pinpoint Test Z.

Chasing Phantoms
Pinpoint Test Z is designed for use with vehicles that have intermittent concerns or phantom codes that might require you to road test them extensively in an attempt to see the concern by recording data on the scan tool. The question a tech needs to have answered is what data should be recorded while road testing? With today’s PC-based scan tools, you easily can record dozens of PIDs and still get valid data. This was not always the case. Back in the days of the Ford NGS scan tool, when you recorded more than four PIDs the ability of the scan tool to capture data significantly degraded.

But even with today’s tools, recording only those PIDs that are most likely to show the concern is still desirable, especially as there isn’t much point in watching various inputs or outputs that have nothing at all to do with the concern.

This image shows a resistive short in the MAF sensor feed to the PCM. How do we know that it is a short and not airflow change? Can airflow change that suddenly? We see a half-volt drop in about 1 second of time. Airflow can’t change that quickly. This is a no-code concern found using Pinpoint test Z.

Let’s take a look at when you’d use Pinpoint Test Z on a Ford, keeping in mind that similar procedures will work on other manufacturers as well. There are four things that you should do to every vehicle that comes through the door and may be done in any order you choose.

Step one: Attempt to verify the concern exists as stated by the customer.

Step two: Perform a good visual inspection.

Step three: Check for related service information and Technical Service Bulletins (TSBs).

Step four: Begin your troubleshooting initially with nonintrusive tests.

This is where you might run into your first real hurdle to fixing the vehicle. Yes, these computers are very good a finding the correct faults, but they are not perfect. Failures within operating parameters of certain components will cause concerns to show up as other problems.

In the first step of Pinpoint Test Z the technician is reminded to reset the PCM so that data stream can be accurately recorded.

Here’s an example. My brother-in-law brought over his 2009 Ford Flex with a trouble code indicating that the upstream wideband air fuel ratio sensors were bad. In fact, the Mass Airflow Sensor (MAF) was contaminated and the real cause of the concern. I used the principles taught by using Pinpoint Test Z to figure out this concern.

Ford’s starting point for all driveability analysis is Pinpoint Test QT1. This pinpoint test covers what any good initial drivability diagnosis should. There are a number of things that you need to confirm before you do any serious analysis of any vehicle: fuses, quality of fuel, mechanical integrity and others just as they are listed in the QT1 test procedure.

When looking at QT1, the first thing you do after getting the vehicle ready is to scan it for any Diagnostic Trouble Codes (DTCs). Of course, if you have codes, you review them first and do an analysis of the concerns by code. If there are no codes, Ford directs you go to Symptom Analysis. When you are doing symptom analysis, you are not sent directly to Pinpoint Test Z. That might be several selections down the list of things to do. At this point, keep in mind that any record of DTCs might be real concerns and/or they may be a symptom of another problem. You may be sent to Pinpoint Test Z from any one of the other pinpoint tests.

Cause or Effect
Once you are directed to do Pinpoint Test Z, the first steps might ask you to do several things that seem redundant, like clearing any set codes and test driving to see if they reset. The next steps of the test are instructions on road testing and data gathering, while the remainder of the steps are instructions on wiggle testing.

There are two sets of symptom charts in this part of the manual. The first gives you a symptom and then tells you which chart to go to for analysis.

The second is called Reference Value Symptom Chart, and this one tells you which category of PIDs you will select based on the symptom.

From there you go to the Reference Value Parameter Identification (PID)/Measured Signal Chart to get the PIDs for recording. This can be a bit confusing at first, as Ford uses hyphens in between numbers in their lists. You may see something like this: 1-4-7-10. Most of us are used to seeing a number series like 1-4 and interpreting that as being 1, 2, 3 and 4. That is not what they mean. In this example, you would select this PID for category 1 and 4 and 7 and 10.

It looks like this:

Let's look at a couple of important considerations in using this test. First and foremost is that Pinpoint Test Z is written to be year specific. It is true that if you have a hesitation on acceleration on a 2004 Focus that the PIDs, you will be directed to view for that model year will be very similar to the ones for a 2012 Focus. However a 2012 Focus has gasoline direct injection and 2004 does not. There will be different things to view for each.

In fact, if we go back to Quick Test 1 there will be different things to check just to prepare the 2012 for testing versus the 2004.

Step two has you setting up your scan tool with the appropriate PIDs for the concern. Step three is asking you to verify the symptom to assist in making a correct analysis.

Once you have your recording comes the analysis. For this you turn to Section 6 of the Ford PCED or whichever service information source you're using, and find the PIDs you've monitored. Section 6 are Reference Values for each engine and gives typical values for PIDs at idle, low load, and high load driving conditions.

The real art to intermittent diagnosis comes from trying to determine whether the PID values that you see when you record an event are the cause or an effect. Let’s take an example to show what I mean. You are driving a car that has intermittent hesitation. The vehicle acts up while you are driving it and recording the event with a scan tool.

How many PIDs are going to show the concern? If you answered more than two you are correct. Which ones do you concern yourself with? You look at PIDs that have higher authority than others. Which sensors are higher authorities in getting the Powertrain Control Module (PCM) to make changes? Does the fuel pulse width commanded make changes in the oxygen sensor signal or does oxygen sensor signal make the PCM change the pulse width? The oxygen sensor signal is an input to the PCM and therefore is more likely to be the cause of a concern than the fuel pulse width commanded.

Once you have determined which category to use for analysis and you are in test Z2 you may go through this chart and select the PIDs related to your concern.

Fixing the Flex
To explain this, let’s go back to the case study on my brother-in-law’s Flex. Why did I look at the MAF sensor? Certainly a faulty HO2S might cause a problem and it is a fairly high authority input. Let’s think about how the system works. The PCM uses the HO2S to determine if the air/fuel ratio is at stoichiometric or not. The PCM makes changes in operation based on the input provided by this sensor. Is there any sensor that may be even more important or have higher authority than the HO2S in terms of engine operation?

I did the inspections and went to QT1 and tested the vehicle. The vehicle had an illuminated Malfunction Indicator Lamp (MIL) and codes. I looked at the codes and then I looked at Freeze Frame data. The codes were all set at idle. I got into the service manual and looked up the codes and their typical causes as well as the test procedure to analyze the fault. It was a code for an inoperative wideband sensor.

The first thing to do was to verify the codes by looking at the operation of the sensors. The fuel trims were around 29 percent positive at no load idle. As I increased the engine speed, the fuel trims started coming back towards zero percent, some of the more classic symptoms of either a vacuum leak or a contaminated MAF. In the case of an air leak, the fuel trims will be very high at idle and drop towards normal at higher speeds.

This chart gives you the category id number that you will use as you select PIDs in the Reference Values Chart. 

As soon as I saw the fuel trims react, the DTC no longer was valid as it detailed a faulty sensor. Now it’s an opportunity to use Pinpoint Test Z. Using the charts, I pulled more PIDs and began to look for other concerns. Knowing how these systems work, the first PID I looked at was the Barometric Pressure (BARO) PID, which is from the MAF sensor and reports as a frequency.

In the case of the Flex, the MAF was telling the PCM that less air was entering the engine than actually was. The PCM took the faulty information and added the amount of fuel that it thought should be enough. This resulted in a mixture that was too lean for the operating conditions. The HO2S sensors were not faulty and therefore read the lean A/F and sent a signal back to the PCM to richen the mixture. The PCM did this and continued to add fuel up to its limit that was still not enough to get the sensor to switch. It set a code.

A contaminated MAF usually will swing from under reporting airflow at idle to over reporting at high speed. I never took the car on the road to see what it did, because as soon as I saw the HO2S start to switch as I brought the RPM up and the fuel trims dropped, I knew the wideband sensors had to be working.

The fastest way to check the condition of the MAF on most Fords is to look at the BARO PID and see what it is. In this case it was reading 152Hz. I live in Grand Rapids, Mich., about 500 feet above sea level. The BARO reading in frequency for Grand Rapids should be no less than 155 to 157, depending on weather conditions.

These charts are engine specific and give you expected values for different operating conditions and the units that will be displayed on the scan tool. You may also use these values to use when testing with other tools.

That information has most often been found in the pinpoint test for a MAF code. There is a table of frequency to altitude. Variation of 3Hz or more is cause for concern. When you do a Keep Alive Memory (KAM) reset, the value will be 149.7Hz. When the MAF loses power or the PCM loses its memory for any reason you will see this number. What this represents is the default value the Ford uses when it is reset and represents about 3,000 feet above sea level. This number was picked because most of the country is somewhere between 5,000 feet above and sea level, and this falls somewhere in the middle.

We cleaned the MAF and cleared codes and KAM. The vehicle was fixed.

The principles of Pinpoint Test Z are used regularly by anyone analyzing a vehicle with a concern to determine whether the code is true or phantom, is a failure within operating parameters or an intermittent concern that shows up only on a Tuesday.

But you can also use it to learn the relationships between inputs and output and how these cars work. What was seen on the recording I made of the Flex stood out if the tech knows what to look for. I have seen many technicians stare at a trace on a scan tool, the concern as big as life but they could not see it because they did not know what normal looked like. If you don’t know what normal looks like, if you don’t understand how things work then not even Pinpoint Test Z is going to help you fix that broken car. 

Subscribe to Motor Age and receive articles like this every month…absolutely free. Click here