You’ve probably already figured out that the two codes mean you potentially have two separate problems, but either one of them could cause your car to switch to limp home mode. In any case, they both need to be fixed.

So, let’s start with the PO118 code. This suggests you have a faulty engine coolant temperature sensor. When this fails, the computer isn’t getting the information it needs to know whether the engine is cold or warmed up. As a result, the fuel-air mixture will be all over the place and the vehicle will possibly use more fuel and run poorly as well as being hard to start in the morning.

The other fault code you’re seeing, PO489, is to do with the engine’s exhaust gas recirculation valve. This valve channels some of the engine’s exhaust back through the combustion chambers to reduce tailpipe emissions by burning the same gasses twice. Your car’s computer will be constantly opening and closing this valve, but it’s an electrical signal (from a sensor) that tells it when to do so. If this sensor has failed, that information won’t be getting sent to the computer and the check-engine light will come on.

Both of these faults will probably be fixed by replacing the sensors in question, but until they are replaced, the car will continue to throw fault codes and switch to limp home mode.

The Territory is pretty well known in the fixit trade for having various transmission problems. Perhaps the most common was a failure of the entire transmission due to coolant from the transmission cooler mixing with the transmission fluid inside the gearbox. When that happened, the destruction was fairly complete with ruined electronics and internal hardware as the contaminated fluid could no longer satisfactorily lubricate the gearbox’s many moving parts. A whole new transmission was the usual outcome.

The first sign of this was usually milky transmission fluid (caused by the water mixing with the oil) but by then, the damage was often already done. This was more of a problem with the later model Territories with the six-speed ZF automatic transmission.

The first thing to do is get your mechanic to drive the vehicle when it’s hot. Arrange a time and then deliver the car at that time with everything up to full operating temperature. Otherwise, the problem isn’t going to show up when it needs to.

While there are lots and lots of things that can cause this sort of behaviour, it does sound like something in the actual powertrain is the problem. That’s because the shuddering goes away when you drop the transmission into neutral and let the vehicle coast to a stop. If the problem was a wheel, a wheel bearing, axle, brake problem or an out-of-balance driveshaft, the problem would continue even though you were coasting.

You may have a problem with something inside the transmission itself, way too much backlash somewhere in the driveline or a problem with the torque converter. Either way, you need to have your mechanic experience the problem or everybody is simply guessing.