Fault Code P0170

[alexlintern]

Hello - A 2001 C5 Break 1.8 petrol 16v will now not start  :(

 

The engine cranks but will not fire.

 

X431 diagnostic shows the following:

 

p0170 Fuel injection - intermittent fault

 

There is also a fault stored for 'richness regulation intermittent fault'.

 

Before the non-start problem the car has been suffering from poor power and also from a bad misfire (possible EGR valve?)

 

The EGR valve was removed and cleaned which gave a short term improvement.

 

Now the car will not start and I want to ask if anyone has experience of cleaning the MAP air mass sensor (this seems like a common cause of failure) I cannot see how to remove the air intake elbow after the 

flexible coupling from the air filter box. There seems to be a hidden screw somewhere!

 

I have also read that C5 will not start if one injector is faulty and the ECU gets a low pressure reading from this circuit. Is this correct????

 

What can the DIY er do next?

 

Thanks for any help and advice offered! 

Edited March 24, 2015 by alexlintern

[paul.h]

Welcome to the forum.

 

On here P0170 is given as

P0170 Fuel Trim Malfunction (Bank 1).

 

Often bank 1 means inlet so this could possibly be a problem with the exhaust catalyst inlet lambda sensor. To check it you would need to run the car and see if this sensor is switching using live data. However, I am not sure if a problem with a lambda sensor would prevent the car starting.

 

First thing you need to do though is check if the fuel pump is running - can you hear it in the fuel tank when you switch on the ignition? If this is working and delivering fuel then it could be something such as a faulty crankshaft position sensor that is preventing starting.

 

Haynes does not mention a fuel pressure sensor for the 1.8 petrol. I had a C3 that sufferred a fuel injector failure and that still ran but with a bad misfire and put on the engine management light - so possibly you may not have a fuel injector problem.

 

According to the Haynes manual the MAP sensor is on the front of the inlet manifold and in a photo can be seen without having to remove anything else and Haynes does not say anything else has to be removed to get to it. It is held by a bolt so could be removed and checked for any blockage. I think they are not expensive if you need to replace it.

 

To remove the elbow Haynes says to first remove the flexible section and then insert a screwdriver through an access hole next to where the flexible was fastened so a clamp that holds it to the throttle body can be slackened.

[alexlintern]

Very sound advice, thanks! Fuel in tank and pump runs to prime fuel system pressure. The MAF sensor part is Bosch 0-261-230-057 and is located in the swirl manifold. I am presuming that no signal from a crank/cam sensor would deliver a subsequent fault code; it could however explain why the motor will not fire! Fuel + spark = GO until the electronics get inputs. I am now wondering what the ECU read when starting.

[paul.h]

The Citroen part no. for the MAP sensor is 1920AN if you have a manual throttle body or 457403 if you have a motorised throttle body but you should check this using your VIN. On the citroencarparts.net site they are about £50. Note your car does not have a MAF (mass air flow) sensor and just uses the MAP (manifold absolute pressure) sensor. The cam sensor is 19208W (£63) and the crank sensor 1920EN (£12) - was 19207N to RPO 09278 and 1920FP from RPO 09279. Again check using your VIN.

 

A crank sensor may not give a fault code but we had a cam sensor fail on a C3 that gave a code but it still ran, possibly since there are 2 cam sensors on it but it ran in limp mode.

 

A code reader with live data should also have freeze frame data when the fault code occurred which may give an indication of the fault cause if not obvious from a fault code. You could also measure the resistance across the crank and cam sensor pins and if open circuit could indicate a fault.

[alexlintern]

Thanks for the valuable info! Very kind of you. The absence of MAF will end my headscratching about where the blessed French have hidden it hehe. I am now thinking that the crank sensor is possible however the fault code p0171 fuel injector fault. There is a split in the breather pipe from the cam cover to throttle body air intake which may cause the ingress on additional unmetered air to cause the lean fuel mix and the injwctor fault code. An air leak will cause severe long term problems in older engines. A new car would be great!

[alexlintern]

MAP sensor part no is 0-261-230-057 Made in Germany (Bosch part)

 

I shall try and locate the crank & cam sensors to measure resistance values; any clues on their locations much appreciated.

 

This is a nuisance!

[paul.h]

Citroen use different part numbers to the manufacturer ones which are stamped on the parts and are often the better ones to use when searching the internet. You can get the Citroen ones from the parts diagrams which are available as a free service on the service.citroen site if you register as another professional and a member of the Citroen Owners Club. Then use your VIN (VIS) top left to find your car. The engine sensors can be found under Mechanical, air and fuel suply, INJ calculator sensor BVM (assuming your car has a manual gearbox - BVA is an automatic one) http://service.citroen.com/do/changerParametres

 

If you intend to keep the car and do your own maintenance the Haynes C5 workshop manual is worth buying. From this the crank sensor is located on top of the clutch bellhousing and is held by 1 bolt. The camshaft sensor is located in the exhaust camshaft cover - remove the engine cover, disconnect the crankcase breather hose on the rear cylinder head cover to get to the sensor, it is held by 1 bolt.

[alexlintern]

The non-start traced to faulty crank sensor! located in a hiding place on the bell housing! The sensor sends a signal to the ECM and that runs the fuel pump & injection system. The engine is still suffering from a fluttering type of hesitation and I wonder if the EGR valve is faulty; could this be cause of fault code p 0171? I tried removal & clean of EGR and car seemed to run better for a week. I had intermittent fuel pump problem before replacing the crank sensor. 

[paul.h]

In the Petrol Diesel and LPG Injection section on here, P0171 is listed as

P0171 Fuel Trim System Lean (Bank 1)

 

So again this could be the exhaust inlet lambda sensor. If your code reader does live data, see if the lambda sensors are switching. The inlet one readings should switch frequently (every second or so) and the outlet one should stay steady provided the catalyst is ok. Also look at the temperature sensors, the engine coolant should be the outside temp when the engine is cold but about 95°C once up to temp. The inlet air one should be the outside temp and once the engine is hot should be a bit higher.