Electronic Diagnostics
Tracing and fixing faults in electronic engine management systems
Rover’s 25/45 and 200/400 series cars were notable for employing the overhead camshaft K-series engine in the petrolpowered version. Kim Henson and Edward Haggar examine a 2002 example.
The Rover 25 evolved through several models from the original Rover 200 four-door saloon range. From 1984, the first Rover 200 models were based on the Honda Ballade but, from 1989, the second-generation 200s featured more individualistic Rover styling. This generation included three- or five-door hatchbacks, originally intended to take the place of the Maestro (although the two ranges continued together for several years), while 400-series cars were saloons – estate variants were added later – which effectively replaced the first-series 200 saloons.
Particularly important for Rover was the use of their new belt-driven K-series overhead camshaft engine, also used in Metros/rover 100s, but in 1.4- and 1.6-litre capacities for the 200/400 line-up. This replaced the well-respected and long-running A-series engine and was capable of more easily meeting strict emissions performance levels. Its construction incorporated long through-bolts linking the cylinderhead, cylinder block and oil pan.
The third-generation Rover 200 arrived in 1995, with all-new three- or five-door hatchback bodywork.
The Rover 25/45s arrived in time for the new millennium, with many similarities to previous models but with some bodywork restyling and revised running gear to improve dynamic response and handling, which had already been widely praised in the outgoing 200/400 variants. Some versions were fitted with Steptronic/stepspeed semiautomatic clutchless CVT transmissions.
From late 2000, 1.1-litre K-series engines were offered, in addition to the larger-capacity units.
It is interesting to note that the K-series engine was sold in eight- and 16-valve forms, the latter units providing particularly spirited performance. The 1.8-litre 16-valve motor used in some
versions was especially popular due to its eager power delivery.
The cars were upgraded during 2004, but Rover went into administration in April 2005. Nevertheless, there are many surviving examples of the 200/25 and 400/45 series cars, plus the MG ZR and ZS models based on them, that continue to give reliable service and, in the future, are likely to be regarded as modern classics.
The subject of this feature is a 2002 Rover 25 with a 1.6 petrol K-series mated to a six-speed Stepspeed clutchless transmission. It uses a Rover MEMS 3 management system. Edward Haggar is our guide to this model.
Preparation
There are few modern cars that are easier to service by the DIY mechanic than the Rover 25/45 and the previous 200/400 models. The air filter element can be reached and renewed after simply unclipping the housing, and replacing the fuel filter is simply a case of releasing the inlet and outlet pipes (14mm spanner). The oil sump plug is readily accessible with a 15mm spanner, and the oil filter is also very easy to reach, being right in front of the operator. The spark plugs are hidden beneath a cover panel, but it takes just seconds to undo the securing bolts with an 8mm spanner. There are certainly no excuses for poor or skimped maintenance on these models, as routine servicing is so simple.
Even renewing the cambelt and water pump is easy and it’s advisable to tackle both at the same time because the water pump is accessible while the cambelt
is removed. The camshaft locking tool is readily available and inexpensive, and replacement parts for the K-series motors are generally cheap to buy.
Unfortunately, due primarily to the design and construction of the original cylinderhead gaskets and the plastic dowels used to locate the gasket on the cylinder block face, these engines have gained a reputation for head gasket failure. It is certainly true that the gaskets can fail at any time and any mileage, especially if cooling system maintenance has been neglected.
When the gaskets fail, the engine oil and coolant can mix and/or leaking coolant can find its way into the combustion chambers, resulting in difficult starting and, even if it does start, the engine may run on fewer than four cylinders until the coolant is expelled. Note: if a diagnostic camera is available, this can be introduced to each cylinder in turn via the spark plug aperture to pinpoint evidence of the failure.
If this potential problem had been sorted properly by Rover at the outset, the vehicles, which were well-received in other aspects, would have had an excellent reputation. The good news for owners is that upgraded head gaskets and steel dowels are available at reasonable prices and can sort the problem permanently with just a few hours of work.
Fault 1 CRANKSHAFT SENSOR
When our first fault occurs with these Rovers, the driver will experience poor starting. Initially, the difficulties might only occur when the engine is hot, but the problem can worsen to the point where the car won’t start at all. It can also cut out when driving.
The beauty of this K-series engine is that a basic multimeter may be the only diagnostic tool you’ll need. A quick check can be made by cranking the engine and looking at the rev counter, to see if there’s a slight movement of the needle. This reveals whether the crank sensor is sending a signal; it shares it with the rev counter.
Next, inspect the crank sensor itself. It can be found at the rear of the engine and access is from underneath. Once you reach the sensor, set the multimeter to the ohms scale and check for resistance; a figure of 1100-1700 ohms is acceptable, but it’s likely you will see open circuit to infinity.
Always renew the sensor with a good quality replacement – Rover parts are still readily available. Many owners will protest that the crank sensor has already been renewed, only for it to turn out that the new sensor is at fault. A multimeter can be used, as well as a borescope and code reader; a ‘P0336’ fault code will likely be stored.
Fault 2 DEFECTIVE COOLANT TEMPERATURE SENSOR
Our next fault results in extended engine cranking, possibly accompanied by the smell of petrol. Essentially, the engine is being told by the coolant temperature sensor to operate with a richer fuel mixture. The key here is that the motor always starts eventually.
Again, a simple multimeter can be used to check this. Set it to the ohms scale and measure across the sensor. When the engine’s cold, the reading should be around 5900 ohms and 330 ohms up to operating temperature. A faulty sensor will show ‘back to front’ readings: when cold it will read 330 ohms, hence the extended cranking. If a code reader is available, check for fault
codes. It’s likely that no codes will be stored because the ECU thinks things are working correctly. If available, read off the live data and you should see an incorrect reading for the coolant temperature sensor.
Fault 3 FAULTY IGNITION COILS
If the vehicle is coughing and running roughly to the point where it becomes almost undriveable, the first check to be carried out is to the ignition coils.
First, remove the cover panel, held via three bolts (8mm spanner). With the engine running, very carefully lift each lead/coil in turn and check for a change in the engine note to confirm a cylinder misfire. Only do this if no diagnostic code reader is available – it is always preferable to use a diagnostic tool. Confirm the fault by performing a cylinder swap with another cylinder to see if the misfire moves.
We recommend that the coils/leads and plugs are all changed in sets. There is no saying how old the other coils and leads are, and if one component in this chain breaks down, the others may soon follow.
It’s worth paying attention to the wiring feeding the ignition coils; the cables can become brittle over time and they are also known to become trapped if not clipped in correctly.
Fault 4 CYLINDERHEAD GASKET FAILURE
The K-series engines run very hot – it was Rover’s way of helping with emissions. Unfortunately, when these engines were being built, they didn’t incorporate a head gasket that was up to the job. There are several different repair methods, but fitting the thicker upgraded type of head gasket from a local factors is probably the easiest.
Using the correct antifreeze is crucial. It should be the red long-life type (OAT) and needs to be renewed more often than normal. In addition, any coolant leaks should be dealt with immediately to avoid head gasket issues. Note that the coolant header tanks are prone to cracking around the top, but are cheap enough to replace.