Holden Reviews

Fault code PO171 usually indicates a lean air:fuel mixture entering the engine. As in there’s too much air and not enough fuel. This creates all sort of problems including poor running, but it could also lead to engine damage in the longer term.

Experience suggests that in this particular engine, this problem is often caused by a vacuum leak, and, in turn, that’s often caused by the PCV (positive crankcase ventilation). Since you’ve changed your PCV (presumably for a band-new one) that probably rules that out, but it would still be worth a check. After that, you need to start looking for leaks in the various vacuum hoses around the engine, and don’t forget to make sure that the dipstick and the oil filler car are both sealing, as these can lead to vacuum leaks, too.

If none of that identifies the problem, you may need to check and clean the air flow sensor. If this is giving false readings, the mixture will be wrong as the engine’s computer is getting poor quality information.

But before any of that, did you reset the check engine light after performing the repairs you’ve mentioned? It could be that simple.

It remains a mystery to some of us why car makers ever switched from the old-fashioned manual levers for four-wheel-drive engagement to the rotary dial or electronic switch type. Pretty much everybody who has owned a 4X4 with the electronic engagement will have experienced a situation where the electronics just don’t seem to want to select four-wheel-drive when they should. This is usually a momentary problem, put right by trying the dial or switch a second time, but it’s still annoying.

Your problem is likely to be a poor electrical contact in either the selector dial or the actuators under the car that physically engage four-wheel-drive and/or low ratio. A quick check under the vehicle might expose a loose wire or broken fitting, but otherwise, a trip to a workshop that knows this make and model is your best bet. The good news is that the problem should be pretty quick, easy and cheap to fix once it’s been identified.

You have two issues here. The first is the transmission problem, and, to be honest, on a late model car like this, an automatic transmission specialist is where you need to go. A slipping transmission can be caused by all manner of things, starting with the simple low fluid level, to the catastrophic mechanical failure. In between there are also electronic possibilities to be investigated.

Your second problem is that you’ve spent otherwise useful money on an aftermarket extended warranty. All too often, these warranties are carefully worded to exclude a range of possible problems you might experience. You might be lucky and the warranty will cover the repairs (it’s definitely worth a try) but don’t be surprised if the fine-print scuppers any chance of the warranty paying out.