Peugeot 206 cooling fan not working! - Another ECU controlled device

2003 Peugeot 206 1.4 Electric Cooling Fan not working

It's an intriguing thought that all over the world there will be Peugeot 206's experiencing this exact same fault. That's because no matter what the make of car, your model will share the same design weaknesses as it's brothers and sisters. 

One such fault with my 2003 Peugeot 206 is the failure of the cooling fan to operate. It used to be that a cooling fan was controlled by a simple thermostatic switch. However, things have now moved on and I've learnt that that this is another function controlled by the ubiquitous ECU. That makes fault finding a little more involved than simply shorting a couple of wires!

Computer says STOP!

The problem became apparent when the car was idling and generally being driven slowly. The temperature gauge showed a rapid increase in temperature and the dashboard stop light activated.

Many years ago engine cooling was provided by a belt driven fan which worked all the time. For greater efficiency viscous couplings were then introduced but in the quest for more efficiency these were replaced by electric fans that would operate only when required and not all the time. There operation is usually a very obvious fan noise from just behind the grill so my first reaction on being alerted to a fault was to listen for the sound of the fan and check the coolant level. Silence and no coolant loss! Therefore, having let the engine cool, I drove the car home for investigation (because when the car is moving steadily the engine gets enough cooling from the forced air flow through the radiator).

First carry out research - Is it a common fault?

It could have been a more serious fault. At the very worst a failed head gasket but my golden rule is to look for the simple and obvious first. This it proved to be.

Having carried out some basic research on internet forums I gathered some general information and one thing I did learn was that the cooling fan operation failure was a reasonably common occurrence and the cause was corroded cables. They corrode because they are in an exposed position behind the grill. Consequently I needed to start examining the wiring which required disassembling the grill components. Work such as this is an awkward task since it's not obvious how the various parts are held together so here's an attempt at highlighting the key lessons learnt.

Removal of grill components

There are three components to remove/loosen to gain enough access. The first is the top, black grill held on by 4 fasteners (already removed in this picture) that just require the centre parts easing out with a small flat bladed screwdriver and then they pull out of the holes.

Then there are two hexagon headed screws at either side which hold the second component which is the red trim panel that holds the badge and goes under the headlight to the wings.

Removing these screws provides enough movement to ease out the black grill which is located to the red trim panel with a row of tabs that can be disengaged with care.

When this is out of the way a star drive screw will be revealed behind the badge that has to be loosened. There is also two very innocuous tabs that have to be disengaged adjacent to inner corners of the headlights. Pressing down on these releases them and enables the trim panel to move forward. The picture below tries to identify what to look for.

This just leaves the fasteners at either end. The ones that hold the trim to the wing. These fasteners, two at either end, push into holes in the wing and should lever out. Three of the four broke in my attempts but it's not a show stopper. A trip to the dealer for the replacement can be made when convenient. The trim is a bit loose without them but not that it is noticeable. Here are some pictures that will hopefully help.

With this panel out of the way I also found it necessary to loosen the black grill below the bumper. Fortunately, this is easy since it is held in place by simple location tabs around it's perimeter. It wasn't removed completely due to the towing eye being in the way but once eased backwards it could be manoeuvred to give enough access to the wiring.

Gaining access to the wiring

Having removed the grills, the compartment that houses the two two relays and associated wiring that operate the fan can then be easily accessed. The compartment is to the left of the fan and the cover is held on by 3 fasteners of the type that require the centres easing out with a screwdriver. The picture below shows the compartment with cover removed and relays loose for inspection.

Corroded wiring confirmed

As indicated by my internet research from support forums the wiring was found to be corroded. In fact one wire was detached at the point where it connected to lower relay. It was obviously not possible to repair and this left two options; obtain another relay socket or remove the socket and put spade connectors onto the ends of the wire in order to connect these directly onto the relay unit itself. The latter was chosen since it was a simple and cheap solution requiring minimal tools.

Important to note that some of the cabling is quite heavy duty and the spade connectors I purchased from the local accessory shop wouldn't accept this size. Also since I don't have a crimping tool I decided to solder the connectors on but this wasn't as easy as I'd expected. It required a heavy duty soldering iron and the copper conductors needed a lot of cleaning to remove the black oxide often to be found in these situations.

Fan still not operational

It seemed in all probability that the fan would now work so I left the engine idling to cause the engine to heat and actuate the fan. The fan still didn't operate! This meant I now had to start thinking and investigate just how the control system worked.

The fan control system

After some investigation the role of the various relays and sensors was deduced. The first component to mention is the engine temperature sensor pictured below.

It's the green object in the picture on the right side of the engine. This is a component that alters it's resistance according to engine temperature. The ECU measures the resistance to determine the temperature and when too high it switches the fan on.

However, disconnecting the sensor makes the ECU think the engine is over temperature and avoids having to run the engine to create the over heating. 

When the ECU thinks the engine is too hot it switches the fan on by actuating the relays described above. In fact there are two relays to achieve a low and high speed of fan operation.

The upper most relay in the compartment powers the fan at low speed. This has a resistance in it's feed to the fan which means the fan is supplied with a reduced voltage. This resistor which is a coil of wire, can be found at the bottom of the radiator housing

The lower relay has no resistance in it's feed and provides the fan with the full battery voltage.

Another important point to note when testing is that the engine must be running to check the fan operation. With the sensor disconnected the STOP light operates immediately the ignition switch is turned BUT it does not bring the fan on. This requires the engine to be running.

Fault rectified

With the cabling problems fixed the final problem was found to be with the low speed relay. It simply needed a gentle tap with the screwdriver to coax it into operation! It's repeatedly tested OK since then.

To sum up

Well it didn't prove to be a very technical fault after all but was made more daunting by the discovery that it was controlled by the ECU.

It has made me aware that there are two separate cabling types on a modern car. Those that are used by the ECU to sense and actuate and those that provide the power. These functions are often reflected in the two sizes of wire encountered. For example, the wires from the ECU that control the operation of the relay  are of light duty whereas the power feeds to the fan that they are controlling are noticeably larger.

Importantly the voltages on these wires are different. The ECU controlled wires being 5V and the power often 12V so it's important not to get them mixed up.

Update on BMW 320D suspected MAF problem

It's been a few months since my last post and this one is just to report that the problem still exists.

To recap the fault code that is being chased down is P3263 which indicates a faulty MAF. But this has been replaced, as has the EGR valve. These replacements did improve the general running but the same fault of erratic, jerky acceleration remains. In fact the performance is once again getting worse. It's time for a fresh look which will be happening soon.

If only I could relate the performance I experience through driving to the operation of the EGR and turbo boost! Perhaps I will be able to be soon through a data logger I'm making in a separate project.

EGR and Turbo Boost Control

In trying to work out what the ECU is detecting that triggers the error code I started trying to understand how the EGR and turbo is controlled. These are my latest thoughts

EGR Control

Why have an EGR valve? In practice, combustion using the exact ratio of fuel to air has some significant problems. The formation of soot, nitrous oxides and diesel knock (explosive detonation). To counter these problems the air is mixed with cooled, inert, exhaust gas to dilute the oxygen content.
When does the EGR operate? The EGR in most modern engines is controlled by the ECU. In order to decide when to operate the valve the ECU must have to know two things. The mass flow of gas through the engine and the flow of air entering from the atmosphere. Since the exhaust gas is being recirculated the two are not equal. However, the volume of gas being 'pumped' by the engine can be calculated from the engine revolutions, engine size, air pressure and temperature. The flow entering from the atmosphere can be  measured by the MAF. So the ECU should be able to calculate and control how much exhaust gas is being recirculated by the EGR valve.
So when does the EGR operate. Unlike a petrol engine a diesel does not have a throttle. A diesel simply alters the amount of fuel to control the power.Less fuel less power, more fuel, more power, up to the point where the quantity of oxygen in the air will burn no more.
As this point is reached the combustion process begins to get problematic as detailed above. The combustion process is at its maximum temperature and air fuel mixing becomes difficult. Therefore a solution is to recirculate the now oxygen depleted exhaust gas back into the engine as this point is reached.
So when the accelerator is depressed it effectively is requesting the ECU to increase the fuel flow. From the engine revs and MAF the ECU knows when the critical maximum fuel to air ratio is being reached and opens the EGR valve.

Turbo Control

Why a turbo? A turbo, like a supercharger, is a way of forcing more air and therefore oxygen through an engine. This means more fuel can be burnt and more power produced. This also results in higher efficiency by utilising some of the wasted energy contained in the exhaust gas.
How does it operate? Most modern turbos use variable vanes on the exhaust side. When closed they create the maximum pressure differential across the turbo and generate the maximum power.
However, under normal driving conditions the amount of oxygen entering the engine will exceed the power and fuel required. Therefore, the ECU will open the vanes and maintain the flow at atmospheric pressure.
However, as more power is requested and the maximum fuel:air ratio that can be achieved at normal pressure is reached, the vanes are closed and the turbo begins to raise the pressure and consequently air flow. Therefore, more fuel can be burnt and more power produced.

Oh dear. Not entirely fixed.

It's puzzling that the MIL light still comes on periodically to indicate the same fault. But the time period between these occurrences is now usually very long and so not as concerning. Sometimes it clears itself and other times I clear it out of curiosity to see how long it will take to reoccur. For example I drove 200+ miles of mixed urban and motorway driving before it relit. It's like I've turned the clock back to when the problem first started.

So to me this indicates the cause has been an accumulation of problems with one still left to be identified. In retrospect I think the major culprit has been the EGR valve not the MAF. Most probably cleaning with specialist MAF cleaner would have been sufficient.

Last time the MIL illuminated was under heavy acceleration. Is this a piece of information that could indicate the cause?

Dashboard MIL still off fitting new EGR valve.

After clearing the error codes on my BMW320D with Torque app the dashboard MIL is still off. What a relief after all the work and investigation that I've carried out. However, the experience does raise many questions.

One of the most important question is the accuracy, or perhaps more accurately, the interpretation of the error codes. It didn't help that the P3263 code generated by the 'P'ower train ECU was very difficult to find documentation for as it appeared to be manufacturer specific. That is, a code created by BMW. Eventually, it was found to be indicating a MAF (mass air flow) metering problem. So the MAF meter was replaced at great expense without fixing the problem! Fortunately, a simple improvised BlueTack test on the EGR valve indicated it was this unit all along.

Much of the work and expense would have been avoided if more information was available on what the ECU is measuring and then calculating to raise an error. It undoubtedly is an air flow discrepancy but not a faulty MAF meter.It appears that it is an error generated by measuring an unexpected airflow value caused by the faulty EGR valve. So, lesson learnt. Don't take the codes so literally.

My overall feeling though is that the manufacturers may have adopted the open standards but only reluctantly.

EGR Valve fitted

The BlueTack remedy on the EGR valve resulted in a significant improvement. In fact so much so that the dashboard engine management light turned itself off for a short period. However, under hard acceleration the car could still generate considerable smoke (to the annoyance of cyclists!) and a replacement EGR was necessary.

An EGR valve has now been obtained from H.R. Owen, North Acton, London via eBay (and who provided excellent service to resolve problems with the delivery). Although it's fitted I've only been able to take the car a short test run as yet. What I'm eager to do is collect the engine data with Torque and see if the air flow/ manifold pressure etc now generate a more orderly pattern of results.

New EGR valve due anytime.

I found that the EGR valve on my BMW 320D is no longer stocked by many of the after market parts dealers so I made a quick decision to buy when I saw one being advertised on eBay.

So the new EGR valve has been ordered and is due to be delivered very soon. I'll be so disappointed and confused if it doesn't resolve the problems.

And just to recap the original diagnosis indicated by the ECU and backed by the dealers diagnostic equipment was the MAF meter. This was replaced but made no difference.