Fail-Safe Cooling (limp mode)

[Adam Janowski]

2015 3.7 with 140k miles and 8,000 idle hours.
I've had vehicle for 15k miles and it's been great.
First time limp mode yesterday - cruising 35mph on flat with throttle barely cracked. Felt medium "jolt" through vehicle and wrench on dash. Gas pedal does nothing at that point. Almost felt like it shifted in neutral, but gearshift was still in "D". coasted off to side of road and engine idle was fluctuating up and down about 500 rpm - didn't sound great. Turned off for 5 min. Turned back on and all was well. Drove home 50 miles with no issue..
again - first time it's ever happened.
I have cleaned throttle body a couple times over the last year - not sure if failing electronically?
engine, trans, and PTU all have fresh and proper fluids.
Have not changed spark plugs as didn't think any issues - still don't think any issues i suppose - get 19.6 mpg avg and power seems ok for a heavy vehicle.

any thoughts / experience with this?

 

[peterk9]

Hi Adam. The Manual doesn't reference "limp mode" however it does mention "fail-safe cooling". This mode which switches the engine to alternating cylinder operation. Page 222 of the 2nd printing. Did you check the coolant level?

Peter

 

[Adam Janowski]

Hi Adam. The Manual doesn't reference "limp mode" however it does mention "fail-safe cooling". This mode which switches the engine to alternating cylinder operation. Page 222 of the 2nd printing. Did you check the coolant level?

Peter

overflow tank coolant on low side of normal operating range with 30* temps this am and engine off since yesterday. It's in line with the level I'm accustomed to seeing in the overflow tank. "limp mode" is my own term.
manual seems to indicate the following for the wrench icon:
Powertrain malfunction/reduced power (RTT)
Illuminates when a powertrain or an AWD/4WD fault has been detected. Contact your authorized dealer
as soon as possible.

 

[ImpactF0nt]

It sounds to me like an issue with a camshaft sensor or perhaps worst case scenario, you've lost compression from a bad gasket. That's just what I'm speculating, you'll need to have the codes read or take it to someone to get it checked out to find out the real problem but my guess is it's probably the camshaft position sensor.

 

[Adam Janowski]

It sounds to me like an issue with a camshaft sensor or perhaps worst case scenario, you've lost compression from a bad gasket. That's just what I'm speculating, you'll need to have the codes read or take it to someone to get it checked out to find out the real problem but my guess is it's probably the camshaft position sensor.

dunno. scanned for codes and nothing.. no CEL ever - just the gear wrench. I'd say more of a trans / PTU sensor fault per what I read in manual, but it's pretty vague. Never happened previously and hasn't happened since.

 

[ImpactF0nt]

dunno. scanned for codes and nothing.. no CEL ever - just the gear wrench. I'd say more of a trans / PTU sensor fault per what I read in manual, but it's pretty vague. Never happened previously and hasn't happened since.

Yeah I'm not so sure what it could be in particular then. Good luck with your problem