This thread is about my 2006 Ford F350 with 6.0 diesel, automatic. Stock electronics, no chip or special programming. Edge Insight to monitor the engine. “Bullet proofed” engine last summer (ARP head studs, head gasket, Bulletproof EGR cooler, blue spring, etc). The truck has around 130K miles on it.

I am a mechanical engineer with good hands on skills, but truly a novice auto/diesel mechanic so please forgive my lack of proper terminology. The shop I am using works exclusively on diesel engines and has been around for many years. They did the “bullet proof” last summer.

I am hoping someone can help us solve an INTERMITTENT no crank issue. To be clear, when the starter cranks there are no issue with starting. This INTERMITTENT problem has been going on 5 months and I now won’t drive more than a few miles from home because the truck has become so unreliable. Sometimes it cranks fine, other times nothing at all. It has been the shop for four weeks this time (three weeks the time before that), largely because the only time it can effectively be worked on is when the problem suddenly shows itself. The problem can then can disappear for days at a time.

The problem first occurred in December. The truck suddenly would not crank one morning. I have an Edge Insight and it was showing some transmission error codes. After several calls to the tech at the diesel shop I use (they were booked up), they guided me to find a low voltage at the transmission connector (I recall it was Pin 21. It is in the large square connector on the passenger side of the transmission). Disconnected this pin showed 0.8 volts, and it should have been 12 volts. I then traced this to “Pin 1” on the PCM (pink/white, 12 volt reference voltage), in the front connector on the PCM, nearest the grill. I was able to plug the transmission connector back in, then slide a needle in along side the wire coming out of Pin 1 and still see this low voltage with everything connected. As I proceed with the rest of the story, this is what I’m calling the “fault condition”, there is low voltage (under 1 volt) on the pink/white wire coming out of Pin 1 of the PCM and the truck protects itself and will not crank.

The fault condition comes and goes. It appears to be somewhat related to thermal cycling or power cycling. It’s often worse when the truck has sat overnight, and seems to be affected more by a cold night. It usually will not occur when the truck has been started for the day (although that has started to occur more recently). Usually if the truck has started it will restart a few hours later. These are generalities and not always true.

I had one time I tried to start the truck one morning, and nothing (no crank). I did NOTHING other than return the following morning and it fired right up.

We (both the diesel tech and I) have had several times the truck is in the “fault condition” and we will feed 12 volts from the positive post of the battery to a needle stuck in along side Pin 1 (PCM) and the truck cranks normally and starts.

When in the “fault condition” the tech has installed two other PCMs and the fault condition persisted so we are fairly certain the problem is not in the PCM.

When in the “fault condition” the truck has had the fan clutch repeatedly unplugged, with no improvement. We are fairly certain the problem is not in the fan clutch.

When in the “fault condition” if the truck is put in reverse, the back-up lights (white lights on the taillights) will not turn on. The reverse lights are apparently on this same intermittent circuit. The reverse lights work fine when not in the fault condition.

When in the “fault condition” the transmission connector can be disconnected (passenger side of the transmission) and the low voltage still occurs when disconnected, so we don’t believe the problem is in the transmission range sensor even though many of the error codes are transmission related.

When in the “fault condition” and I turn the key to start although the truck will not crank, there is no dimming of the headlights or interior lights. There appears to be no significant drain occurring.

When in the “fault condition” it’s my understanding the tech has checked the two output sensors behind the transmission.

We thought that it could have something to do with the voltage to the PCM. The PCM relay has been swapped and the fuse checked.

More recently I have had two times where the truck started fine, then while driving it, the transmission has shifted VERY hard. Though I haven’t confirmed it by measuring voltage at Pin 1 (PCM), my theory is the fault condition has suddenly shown up and when that happens the transmission sensors do not have proper voltage to function correctly. The truck showed codes P0266, P0528, P0706, P0707, P1702 when this occurred. Although I didn’t confirm the voltage at Pin 1 (PCM), I pulled over, shut the truck down and tried to restart and it would not crank. I called for a tow to the shop. An hour later the tow arrived and I tried it one more time and it started right up….uggggg!!! I drove it to the shop where it has been for the past 4 weeks.

If the truck starts right up in the morning the “fault condition” will usually not occur that day, so it has been very difficult to track down.

Two days ago, the tech thought he had it. The truck was in the “fault condition” and would not crank. He unplugged the mass airflow sensor and the truck started. He plugged it back in and it would not crank. He unplugged it and the truck started. On the third cycle the fault condition disappeared and the truck would start up no matter if the mass airflow sensor was plugged in or not. The mass airflow sensor is still of concern to me due to the thermal cycling pattern I’ve noticed. So just because it got better does not mean this is not the culprit.

Yesterday I went to the shop and tried to help out but the fault condition never showed itself. A few things I tried:

I checked the voltage on Pin 1 (PCM) versus the voltage at the driver’s side battery and it ran about ¼ volt lower than the battery.

I put an ice pack on the airflow sensor (to thermal cycle it) while monitoring the voltage at Pin 1 (PCM) but the problem never showed.

I disconnected both batteries (positive and ground) and then shorted the positive and ground wires to discharge any electronics, then reconnected the batteries. I did this twice but the fault condition did not show up.

For a couple hours while monitoring the voltage on Pin 1 (PCM) I tried wiggling wiring, harnesses and connectors all over the truck. There was never a flicker on the voltage.

While monitoring the voltage on Pin 1 (PCM) I turned the ignition key from off to the run position (around 30 cycles), and never saw a low voltage when in the run position.

While monitoring the voltage on Pin 1 (PCM) several times I cycled the shift on the column through various positions and never saw a low voltage when in the run position.

I pulled every fuse and relay in the panel by the steering and the three that totally cut off the voltage to Pin 1 (PCM) were Fuse 22 (Engine Control), Fuse 116 (Ignition Switch) and Relay 302 (PCM). When these were reinstalled the voltage to Pin 1 was back. [Note: I understand the tech has swapped Relay 302].

I pulled every fuse and relay in the panel under the hood (in front of the steering, behind the PCM). None of these had any effect on the voltage on Pin 1 (PCM).

Current ideas:

It could still be the mass airflow sensor and it suddenly healed itself after the engine was started a couple times. We know the problem comes and goes so this is not ruled out.

There is an intermittent short somewhere in the wiring harness [I am questioning why if it is a short in the wiring on the downstream side of the PCM or if it is a marginal sensor why applying 12 volts to Pin 1 (PCM) will overcome it and allow the truck to crank and start.]

Something is effecting the voltage into the PCM, however other than the no crank and lack of the reverse light turning on, nothing else appears out of the ordinary.

There is a marginal ground somewhere (I’ve been told there are multiple grounds though).



The tech says this is one of the worst electrical issue he has dealt with. We have both read numerous threads on various forums. Any ideas would be greatly appreciated! My son returns from the Navy in a few weeks and I’m hoping to be able to pull the boat to take him fishing. Thank you in advance!

 

I had the same symtoms and when they got worse I went under truck and tighten the Electric conectors on the starter. They waren't really lose could only tighten them mayby 3/4 turn but it did the trick havent had any problems sinns then.

Sorry fore bad english I'm swedish.

 

Thank you for your help. We are fairly certain it is not the starter. The truck has had a new starter installed after the problems first began, the old starter was the original and was drawing a lot of current. That did not however fix the intermittent problem we are having.

I used to travel to Sweden on business back in the 1990s. Beautiful country.

 

Ok, it was worth a shot. It seems that there is some bad connection some where! But this is my first Superduty and I havent had so mutch troubles yet!😉 Glad I found this great forum when I started thinking about a ford truck! It is nice here, where in Sweden did you go?
Some Day a long vacation to North America hoppfully will happen! ☺

 

It has been 20 years. We spent time in Stockholm.

 

Update: We are going to replace the Mass Airflow Sensor and see where that takes us.

 

As an update, the truck is now reliably starting after replacing the mass airflow sensor. We haven't had a single issue where the truck would not crank since that was done.

 

Check the wire loom for the fan/clutch connection. We dealt with the same issues and discovered mine was fried, just ordered the new harness $756, I'll let you know in the next couple days once it's complete.