2014 PHEV Slows then Speeds Up While Cruising

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Aug 28, 2015
Tweed Coast, New South Wales, Australia
Hi All,

Following our 2014 Outlander PHEV's 120,000km routine service last May (2021), when it had only 88,100km on the odometer, the car started behaving strangely when cruising on the highway at about 100-110 kmph.

When the battery level indicator in the car dropped to about 35% after travelling about 20km from full charge, the car would inexplicably start to slow down to about 80 kmph, then without any change of the accelerator position or other action by the driver, the car would return to the speed at which it was previously travelling. This behaviour occurred when driving manually, and also when driving under cruise control.

We took the car back to the dealer/service centre and they confirmed the problem, but could not identify a cause, so refered the problem to MMAL. Due to COVID isolation restrictions at the time MMAL did not get around to looking at the car and have provided no report from the OBD readouts passed to them by the service centre.

Chasing up this problem was exacerbated by my being stuck in Thailand until recently and my wife (somewhat technically challenged but certainly able to describe the problem) trying to get action on the matter, with my remote email assistance. The problem persists, but does not happen every trip, unfortunately as if it did it might beeasier to identify the cause. The car is now due for its 135,000 km service,and I'm back in Oz, so I'll be putting some pressure on the service centre to finally resolve the issue.

Has anyone else experience this errant behaviour?

If so, has the cause been identified and a cure successfully implemented.

Other than that issue, which is really a safety issue when travelling at highway speed that now we expect and react accordingly, we just love our PHEV.


I am not totally sure what your issue is, but I had a similar thing happen in a recent mountain trip along French autoroutes. When in cruise control and direct drive was connected and battery was assisting up a long steep hill the battery depleted and the direct drive was not able to maintain seed so the difference between setpoint and feedback grew which caused the PID control to wind up. Then the drive switched to decoupled mode where the revs were able to rise to generate more power via the generator/motors and get the vehicle back up to seed which happened with a very sudden surge of acceleration and overshoot in speed. Understandable why it happened, if not ideal.
Not quite the same, but a long time ago (2014) my late 2013 model suddenly did a full emergency stop on the motorway when on cruise control. Fortunately it did not trigger an accident. My dealer diagnosed a corrupt line of software - but not without help from Japan.
Hi, yes I have had a similar issue. With about 15% left in the battery, the power surges up and down with he pedal in the same position, flat road, until after several surges the petrol engine finally starts and the message "propulsion power is reduced" comes up. Did you have any success with a fix?
Yes, After a long process that was delayed by Covid and mis-communication it was finally determined that the drive battery had defective cells and was replaced. The improvement in performance after the replacement drive battery was installed was surprising, especiallay the vast impact on the regenerative braking, not to mention full charge drive range being where it should.