Posted to Technical Tips Forum on 10/14/2015
2016 Impala Bi-Fuel CNG/Gas Problems
This is another post that will only be of use to G.M.
technicians at the present time.
If you see a 2015 or 2016 CNG Bi-fuel Impala with a
complaint of SES on and will not operate in CNG mode, check
for P125D and P01A9 set current.
P125D is for the alternate fuel high pressure system small
leak detected and P01A9 is for the alternate fuel rail
pressure too high. If you see these codes, command the
alternate fuel pressure regulator through the complete range
of the control valves. If the up response is not immediate
and the down response does not stabilize within 2 seconds,
the alternate fuel rail pressure regulator is sticking.
The leak code is due to the high pressure bleeding through
the regulator when the vehicle is off, causing a leak
detection fault and the increase in rail pressure due to the
regulator leak is causing high rail pressure on start up
after sitting for a time. This sets the P01A9 code. G.M. is
aware of this problem and a recall is forthcoming.
James from Florida