Faulty Temp Readings and Limp Mode?

[WildeTee]

Hey all,
For context, in Alberta Canada where we are currently experiencing unseasonably cold weather, daytime highs in the -26C range. Not awesome but not uncommon either, this is my 3rd winter with the truck and have a new issue I have not had with this truck

Truck started fine yesterday after being plugged in overnight for the cold but within a minute gave me an engine coolant overheat warning and put the truck in Limp mode. I limped the truck into a detached garage where it could warm up a little bit (unfortunately still below freezing) more hoping that it was just a symptom of extreme cold, mostly hoping I could get it out of Limp mode to drive it to Dealer. As of this morning, Truck seems pretty much thawed, and the engine bay is warmish but I am still getting the same issues. I also noticed the truck shows an outdoor temperature of -29C when the interior of the garage is significantly warmer than that.

I am currently waiting on a tow (sometime in the next 8-12 hours if i am lucky) as I am not confident in limping the truck to the dealer in this weather but was wondering if anyone here had any thoughts because if i can get it out of limp mode i can drive it to the dealer sooner, as it is definitely getting checked either way. Although knowing my luck they will pull it into the heated shop, it will sit for a few hours, and then when they get to it everything will be working fine. Timing feels to convenient for it to not be the cold, although it worked fine for several even colder days and through colder nights leading up to this.

Ford App shows multiple Engine light alerts

- Engine control system has detected that two of the engine temperature sensors are reporting temperature readings that differ by an amount greater than expected
- Engine control system has detected the engine has reached an 'Overtemperature condition'
- Powertrain Control system has detected an engine overheat condition. The engine will continue to operate at a reduced power level.

Anyway, open to the fact that I have probably done what I can at this point but figured would see what the internet thought. Thanks.

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[Dahveed]

From the Ranger factory service manual. Your truck is probably employing one of these failure modes due to a failed sensor. At least that would be my best guess.

Fail Safe Cooling

A strategy called Fail Safe Cooling is built into the PCM that will control the engine if it starts to overheat.
Fail Safe Cooling has two modes: A ‘Closed Loop’ mode that relies on CHT sensor and an ‘Open Loop’
mode that relies on ECT sensor. When the engine starts to overheat, the decision to go into closed loop or
open loop mode is made based on sensor availability and sensor failures. Closed loop mode takes priority
over open loop. The reason is that a good CHT sensor is able to reliably track engine block temperature at
all times, while the ECT sensor will fail to do so when the engine coolant is dumped.

Closed Loop Mode

Stage 1 of the strategy commences if the engine starts to overheat. The CHT sensor transmits a signal to
the PCM, which moves the temperature gauge pointer into the red zone.
If the engine is not switched off and the temperature continues to rise, the Powertrain Check Lamp is
illuminated. This indicates to the driver that the engine is approaching critical limits and should be stopped.
At this point DTC P1285 is set in the PCM which can be retrieved using a scan tool.

Stage 2 of the strategy commences if the lamp and temperature gauge are ignored by the driver. The PCM
will start to control the engine by cutting out 2 cylinders and restricting load. The RPM will be limited below
3,000 RPM initially then will slowly be ramped down with time to as low as 800 RPM. Simultaneously the
MIL illuminates. This indicates that long term engine damage can occur and vehicle emissions will be
affected. At this point DTC P1299 is set in the PCM which can be retrieved using a scan tool.
Air is drawn into the deactivated cylinders. This helps to control the temperature of the engine internal
components. The deactivated cylinders are alternated to allow even cooling of all the cylinders.

NOTE: If the driver is using a high percentage of throttle travel (for example, an overtaking maneuver) when
the PCM starts engine deactivation (Stage 2), the deactivation will be delayed for 10 seconds.

NOTE: After 2-cylinder operation has begun, the engine will not revert to 4-cylinder operation, even if the
temperature should fall, until the ignition is switched off and then on again.

NOTE: The MIL can only be extinguished by using a scan tool after the fault has been rectified and the DTC
cleared.

Stage 3 of the strategy will commence if the engine temperature continues to rise. This results in the engine
being totally disabled before major engine damage or seizure occurs. The Powertrain Check Lamp will begin
to flash, indicating to the driver that the engine will be switched off after 30 seconds. This allows the driver
time to choose a suitable parking place.

Open Loop Mode

This mode is entered when the ECT sensor indicates a high engine temperature that is rising at a
dangerously high rate, much faster than expected based on current engine running conditions. This mode
can also be entered when all sensors used in Fail Safe Cooling determination are failed.
When this mode is activated, the PCM will restrict load, and restrict engine speed to below 3000 RPM, then
start ramping engine speed down slowly to as low as 800 RPM and hold the speed there.
At the same time, the PCM will also move the temperature gauge pointer into the red zone and the P1285
code is set.
If the engine is not switched off after a short period of time, the engine will be totally disabled before major
engine damage or seizure occurs, The Powertrain Check Lamp will begin the flash, indicating to the driver
that the engine will be switched off. The P1299 Code is set.
If the driver decides to restart the vehicle, it will be restarted but with the P1299 still set the engine speed is
limited to 800 RPM. This mode can only be reset by clearing the DTC using a diagnostic scan tool.

 

[WildeTee]

Thanks for the info. That definitely sounds like what is going on.

The tow truck just left with my Ranger. Hopefully, they have time to take a look this afternoon, if not appointment is officially for tomorrow morning.

 

[Frenchy]

We're you able to get an answer of what happened?

 

[WildeTee]

We're you able to get an answer of what happened?

Was just coming back with an Update.

Code read sent them to a service bulletin TSB 20-2153 apparently a software issue on some rangers built June 2019 and earlier. They updated PCM software and the truck is back on the road.

I'm just glad we didn't need to order and wait for parts...

 

[Pinecrestjim]

Thanks for creating this thread and for coming back with the solution. My pre-June, 2019 build just copied your symptoms to a tee. Will have it checked out tomorrow.

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