Powerstroke Fan Clutch Causes Engine No-Start

Updated Jan 31, 2019

Powerstroke Starting Problem Caused By Cooling Fan Failure


(Reprinted with permission from : GEARS / April 2013)


by Steve Bodofsky

Some of the best articles come from the field.

Such was the case with a 2003 Ford F350 equipped with a 6.0L Powerstroke die­sel and a 5R110 “Torqshift” trans­mission. The call came into Rod’s Transmission Service in Coeur d’Alene, Idaho, a shop owned and operated by Rod Cayko.

The truck was driving down the road when it suddenly seemed to lose all power.

The owner thought the trans­mission was slipping, so he pulled over to the side of the road and shut the engine off. Then, when he tried to restart it, the engine wouldn’t crank, so he called a tow truck and had it towed to Rod’s.

The Diagnosis

The first thing the technicians did was try to recreate the customer’s complaint. The engine wouldn’t crank with the key, like a dead battery.

They checked the battery with a load tester and it passed. So they decided to jump the starter solenoid; that got the engine to start.

But the starting problem was just the beginning: The computer was in failsafe, so the transmission was start­ing in 5th gear when you put the selec­tor in drive. No wonder the customer thought the transmission was slipping!

A code check revealed these codes in memory: 

  • P006A — MAP-MAF air flow correlation
  • P0336 — Crank position sensor
  • P0401 — EGR
  • P0528 — Cooling fan speed circuit
  • P0706 — Trans range performance
  • P0707 — Trans range sensor circuit; low input
  • U0306 — Software incompatibility with fuel injection control module (FICM)

That’s a lot of codes! Typically with this many codes there’s usually going to be a circuit failure that’s com­mon to all of them.

According the Rod, “the range sensor codes jumped right out at us, so we checked the backup lights. They weren’t working.”

So they checked the PIDs for the range sensor. There were two available, and they remained 0.0 regardless of the gear range selected.

Rod continued: “We raised the rig up and did a visual inspection. It looked like the pan had just been off. A possible red flag? I called the cus­tomer and asked about it.

His buddy and he recently replaced a bad thermis­tor because the temperature gauge had gone bonkers.

He said he ‘read on the Internet’ that a likely cause was a bad temperature sensor, and replacing the sensor did fix his gauge problem. (Got to love those chat forums, eh?)

“I thought they might have knocked the range sensor wiring con­nector loose when they were in there, so we dropped the pan, but the wiring harness was solidly connected.

The problematic range-rooster comb assem­bly looked intact. The pan was spotless and the fluid cherry.

“Okay, perhaps the sensor itself died. We’d replaced several of these rooster comb assemblies for wear issues, but never because the range sen­sor failed electrically. Could this be the first? We plugged a new range sensor in to see what would happen.

“The new sensor also showed no sensor data; just 0.0 on the scan tool, regardless of gear position.”

About then they knew this wasn’t going to be an obvious fix: It was time to call the ATRA HotLine for advice.

They spoke with Jarad Warren, one of ATRA’s newest tech advisors. He sent them some wiring diagrams to help them check for power and ground and, after hanging up, began examining their scan data more carefully.

That’s when he noticed the cooling fan code along with the transmission range sen­sor code.

So Jarad called Rod back and sug­gested they focus on the fan speed sensor circuit. The cooling fan speed sensor and range sensor share a com­mon circuit.


These Ford trucks use an interest­ing and unique cooling fan system. The fan clutch is called Visctronic; it’s mechanical, mounted to the water pump like earlier versions. But the clutch is controlled electrically by a magnetic coil.

The computer  controls the magnetic field and moni­tors the cooling fan speed through a sensor built into the magnetic coil hous­ing (Figure 2).

The sensor in the fan magnetic-coil assembly shares its reference voltage signal and ground with other sensors in the engine control system, including the range sensor.

If the fan magnetic coil assembly shorts, it can pull the applied voltage too low, affecting the signals from the rest of the sensors in the circuit.


How do you check the cooling fan magnetic coil assembly? Easy: Unplug it. The cooling fan’s still there, so the engine won’t overheat during a normal road test.

That’s what the tech­nician at Rod’s did. Just like that, the engine started normally.

After clearing the codes, they took the truck for a drive. The transmis­sion engaged properly in low gear, all shifts were nor­mal, and the only codes that returned were for the fan control assembly.

Replacing the fan clutch assembly took care of the problem.

The customer was thrilled: He’d been told that he’d need a new transmis­sion.

The fan clutch was a preferable repair from a cost standpoint. And Rod’s tech­nicians were heroes, fixing the truck properly without breaking the bank.

You can be sure that customer will be singing their praises whenever the situa­tion arises.

Special thanks to Rod Cayko and his staff for sending us their story and providing the pictures necessary to get this valuable information out onto the street.

Want to learn more about the Visctronic fan clutch? Google “Borg Warner Visctronic – You Tube” and check out some of BorgWarner’s videos demonstrating the system and explain­ing how it works.