2013 Ford F-150 5.0 - Crank no start. Good CKP signal, no tach output.

I am diagnosing a 2013 F-150 with a crank no start condition.  The vehicle cranks for about 2 seconds (I count two complete engine revolutions by listening to the compression pulses) and then stops.  I believe the normal crank time is closer to ten seconds.  

My issue seems to resolve around the fact that the PCM will not communicate Engine RPM.  So far the PCM has communicated with a scan tool (Forscan hardwired to my laptop, but I have also tried my XTool scan tool to verify results obtained in Forscan).  I have scoped Crankshaft Position Sensor signal at the PCM connector and the waveform appears to be clean and have an amplitude similar to other vehicles (compared against a scope waveform on a running car with the same engine found on YouTube).  However, the PCM will not output Engine RPM data while cranking, nor does the tachometer move on the dash at all when cranking.  There is no spark.  The fuel pump does not activate while cranking, although it does prime when the vehicle is turned on.

I do not think the PCM is shutting off during cranking because I am able to obtain other data during cranking, such as a a "start mode active" indication, as well as throttle position/accelerator pedal position data and Mass Air Flow data.  I have also installed a brand new battery in the truck twice.  

The engine does not seem to have any mechanical issues preventing it from starting: out of the hundreds of times I have cranked it over, it has started twice, both quite soon after battery replacement.  I replaced the battery with another brand new battery and am unable to duplicate this result.  

The other possibly relevant info from the PCM is that the ENG_IMB_STAT (Engine Immobilizer Status) PID reads LOCKED.  I am not sure what to make of this as there are no codes indicating immobilizer engagement.  In an attempt to see if the chip key (I have only one key) is working properly, I removed the ignition switch and turned the key with the chip in proximity to the transponder and without.  Without the chip close to the transponder, the engine will not crank at all.

I have no consistently occurring trouble codes.  I have produced various codes by disconnecting/reconnecting the battery, but once these are cleared, cranking the engine does not produce any codes.  

Any ideas are much appreciated! 

I should also add that after performing the Key On Engine Off Self Test, I get the following codes:

P1288 - Cylinder Head Temperature Sensor Out of Self Test Range

P1711 - Transmission Fluid Temp Sensor Out of Range

U0422 - Invalid Data Received from Body Control Module.

The last of these is interesting to me, as the Body Control Module controls the immobilizer/Passive Anti Theft System (PATS), but I am not sure how to go about tracking down the problem.

PATS Description and Operation: PATS prevents the engine from starting by disabling the starter relay and fuel injector operation. If an unprogrammed key is used or if there is a PATS system concern, STARTING SYSTEM FAULT is displayed in the message center and the engine does not start. PATS cannot disable an already running engine.

Perusing identifix and expanding search criteria, I found this nugget on a 6.2L 2013 F-150:

No Start, No cranking RPM No cranking rpm, Signal good to ecu, Unplug Fuel pump module, got RPM. I got to this point after I had installed used ecu and had it programmed. Truck had cranking rpm with used ecu and programmed lost rpm signal. No codes, Hope this will help someone, I went insane. Fuel Pump Control Module

Worth a shot I guess.

That was my impression of PATS as well: it would disable cranking entirely. However, the Forscan PIDs tell me that the engine is disabled. Is there a different security logic than PATs that I am missing?

No improvement unplugging FPCM. Thanks for looking, though.

Does your check engine light go out when you are cranking the engine over?

Check engine light does not go out when cranking.

Well -with fords the check engine light should go out while cranking. If it does not you are not getting a crank signal.
Or you could have a wiring problem.

Crank signal has been scoped at the PCM. PCM connector inspected and cleaned. What else can cause no crank signal?

Any thoughts on why my engine immobilizer PID shows engine start locked?

I am inclined to believe if scanner shows engine start locked, believe it. I would find out what has been replaced or repaired on this vehicle before you did anything on it. Here is how the PATS works on my 2007 Ranger. Key on- pats light come on and goes out. On engine shutdown- pats light flashes 5 times and goes out. I am not saying that is how yours would work, simply stating what mine does. Another quick note from the ford manuals I have -original manuals state - do not put aftermarket remote start systems on this vehicle. Not sure if what you are working on has remote start installed on it.

I am just thinking out loud with this. As you stated your engine immobilizer pid says engine start is locked- is that why your check engine light is not going out while you are cranking the engine? Any other ford I have ever seen the check engine light will go out during cranking. Perhaps some others have some thoughts on this.

I can't find any information regarding a PID called "ENG_IMB_STAT" on google nor in service info on PATS. The service info does point to a BCM PID "START_ENABLD" and it should say "Enabled" if everything's hunky-dory regarding PATS. I believe there's also a PCM PID "PATSENABL" which should also say "Enabled" but this PID was not mentioned in the PATS service info.

This pdf seems pertinent as well: www.fordservicecontent.com/ford_content/...ats_job_aid_2013.pdf
 
My understanding on the bullet points, the first one being the Check Engine Light being on (while cranking I assume) would seem to indicate that there's no RPM signal. The second bullet, if you had no communication with the PCM then PATS would be the least of your worries, and lastly, you have no PATS codes in the BCM, right?

Did the CKP signal have a DC bias voltage of 2-2.5V on both the CKP+ and CKP- ? I believe this is the floating ground type VRS and that would mean there will be a signal on both wires. Was this checked? In the CKP+ signal did the crank index have a rising edge? Was the peak to peak voltage while cranking at least a volt?

 

Your assumptions about the bullet points are correct: Check Engine Light on while cranking and no RPM signal on the scan tool, I have communication with the PCM, and no PATS-related DTCs. I have seen the PATS job aid and I have been able to successfully reprogram two keys. PATS seems happy.

I am interested to hear that your search also turned up nothing for the ENG_IMB_STAT PID. This PID was found on Forscan. There are also PIDs for ENG_STRT_DIS: Yes and ENG_STRT_NRML: No. So there are more than one similar PID with consistent readings, but it seems these are not commonly known about. I thought maybe this is some PID in Forscan that shouldn't be there, but my other scan tool (XTool D7) also was able to access the same PIDs with the same results.

The START_ENABLD PID in the BCM you mentioned reads Enabled. The PATSENABL PID in the PCM reads Enabled. Everything looks good, I can’t see any contradictions except for the lack of RPM signal and the immobilizer PIDS. I’ve also noticed that the Fuel Pump is not being commanded on while cranking, which I assume derives from the lack of RPM signal, as the pump primes when the key is inserted in the ignition.

I agree that it seems like the Check Engine Light does not go out because of the lack of RPM signal.

Thanks for this specific advice regarding the CKP testing. I have been in the process of double-checking my CKP tests today, and had resolved to double check each leg of the CKP for output before seeing your post. My earlier test of the CKP (described near the beginning of this thread) was attaching the positive scope lead to CKP+ and the negative scope lead to CKP-, which produced a strong waveform over well over +/- 1 volt. I have now attached another probe to my scope and looked at both legs of the sensor at once. It appeared CKP- was not producing any waveform at all. I traced this back to a wiring issue between CKP and PCM (poorly seated connector on the sensor from previous testing). Pulse from both CKP+ and CKP- was verified by scoping the sensor with two channels. No change in starting. After remedying this problem, I noticed that the amplitude of each waveform is now a little less than +/- 1 volt. Could this be not enough? I will try to find a way to post a capture here, which may help with my next question: what is meant by "a leading edge?"

In response to your question about bias voltage: I checked for bias voltage and found only .5-.6 volts on each leg of the CKP sensor. The spec given in my manual is 1-3 volts. I checked by measuring voltage between CKP+ and ground and CKP- and ground. I double checked this value a little later and only found each wire to have only 180 millivolts.

I also found one other odd result: I measured 1.7 kOhms resistance between the CKP shield wire and ground (spec states less than 5 Ohms) . The CKP shield is grounded through the PCM, and I have not found any excessive resistance in the PCM grounds, so it seems there is excessive resistance in the portion of this circuit within the PCM. Could this point to an issue with the CKP/RPM circuit in the PCM more generally?

Thanks very much for the attention everyone has paid to this thread so far.

Most recent capture of CKP signal measured at PCM connector can hopefully be seen here:

drive.google.com/file/d/1gSOOERQn5ofAQAx...18/view?usp=drivesdk

 

I volt peak to peak voltage is achieved here which I circled. The sensor is doing it's job, the computer however is not. If your scope ground was at the battery negative your capture shows no DC bias from this computer. CEL doesn't go out while cranking, no RPM according to computer and missing 2 - 2.5 volts from the computer and you checked the connector? Looks like a bad computer to me.

Correction: you have 2 volts peak to peak which is very good.

The CKP + leg should have a rising edge and CKP - should have a falling edge. I have seen case studies on YouTube where is the wires were swapped it could cause a no start.

I don't think you have to worry about a short to ground as the voltage produced by this sensor is with well within expected norms. Check pin fitment at the computer one more time.

lmg866 wrote:

In response to your question about bias voltage: I checked for bias voltage and found only .5-.6 volts on each leg of the CKP sensor. The spec given in my manual is 1-3 volts. I checked by measuring voltage between CKP+ and ground and CKP- and ground. I double checked this value a little later and only found each wire to have only 180 millivolts.

 

www.aeswave.com/uTest-Advanced-Terminal-Test-Kit-p9748.html
 
This uTest Terminal Kit has a variable resistor.

As a proof of concept, I have not idea if this will work or not, try using a variable resistor, dial in the correct resistance to get 2.5V from a 5V reference circuit and put it into this ckp circuit.

Interesting idea with the adding 2.5 volt reference to the CKP circuit.  While we are focusing on the issue of bias voltage, I'll clarify that I checked for bias voltage by measuring with positive multimeter lead at CKP+ and negative lead at battery negative, then postive at CKP-, negative at battery negative.  At this point I have measured three different voltages using that test: .5 volt, .18 volt, and .2 volt.  The capture I uploaded before was with scope negative leads detached--I guess this was my uneducated interpretation of the term "floating ground" .  Another capture is attached with scope channel 1 positive at CKP+, scope channel 2 positive at CKP-, and both scope negative leads at battery negative.  
 

It seems the the red trace, CKP+, has now lost its amplitude. It should mirror the blue signal.

What changed?

Can you get the red channel signal back by unplugging the computer and jumping the load side contracts of the Starter Relay inside the battery junction box? I have a sneaking suspicion that the computer's messing with that CKP+ signal.

Your scope captures look like a failing crank sensor. You said you get an initial fuel prime when turn key on. The computer will not turn on fuel pump cranking if it does not see an rpm signal. Your check engine light stays on while cranking. Not saying that is it, but your symptoms are pointing at the crank sensor.