LIMP MODE Q&A

LIMP HOME MODE

When I initially bought my VW Polo 2.0L she was a thrill to drive. Her speed was instant, cornering was really good and road holding never better. She was a joy to drive, very unlike my VW Golf II, but then I started getting car troubles,  which were many and varied. My first encounter with VW agents was a disaster. After they "repaired" my EPC fault they charged me a ridiculous sum of money, only to experience the same EPC problem the following day.  After speaking to several of their mechanics, who collectively were unable to fix my car, I came to realize  that I was either far more knowledgeable about automotive electronics than all of them put together, or they knew very little about electronics.  This just put me off the agents completely and when I took my Polo to independent mechanical workshops,  I found the same to be true. I still remember how lost I felt when my VW Polo went into limp mode the first time and the second and the third and the fourth. I felt lost, stuck on the freeway, late for meetings, frustrated and miserable because I couldn't repair her like I did the VW Golf II due to the fact that the Polo had OBD-II. I  thought my VW Polo to be unreliable, there was a point that I feared driver her at night, and later started to hate  even diving the Polo.  I was literally on the verge of setting her alight. But them I decided to buy a Ross Tech cable and downloaded their VCDS and my Polo is a joy to  drive once again. The rest of this blog is devoted to 10 vehicles owners who have experiences similar trouble with their VAG vehicles ranging from Drive by wire problems, to EPC trouble, to DTC trouble Codes to CAN-Bus-issues to name but a few. 

DRIVE BY WIRE
Steve sent this:- Had the problem of no power, tried the technique described in your blog (disconnect battery, wait, reconnect, turn ignition key, wait, turn off, turn engine on, wait, press throttle...) - and it worked beautifully. Many thanks for your help, very much appreciated - particularly as you've probably save me many pounds. 

QUESTION? - DRIVE BY WIRE
Anonymous sent this:- I have a '07 Polo 1.4 16v BUD. I don't have any lights on the dash, but the engine seems really weak through mid revs and is using a bit too much fuel. When I hook up my OBDII there are no faults recorded but when I view the throttle position in real time it doesn't seem to open in a linear manner. As I press the pedal on the road, the throttle valve seems to open slower than the position of  the pedal. eg; 50% pedal = 30% throttle position, 80% pedal = 35% throttle, 95% pedal = 40% throttle, 100% Pedal = 100% throttle. As you can see WOT does give WOT at the throttle body, but I don't generally drive with my foot planted on the floor. I am confused why it does this as you would expect the throttle body to open the same amount as the pedal, could it need alignment? I am loathed to take it to the VW dealer for fault diagno$i$ so if anyone has any ideas????  Thanks 

ANSWER!
On drive by wire model vehicles the throttle doesn't open like legacy cable throttles because its electronically controlled. 

DRIVE BY WIRE
Durell  Dunn  left this:- I am currently experiencing the same problem with my 2003 polo,1.4. The car goes into limp mode and on some occasions switches off in traffic, hectic ! I will use your method. Thank you for saving me from going to a VW dealership, all I can do at this stage is do and hope 

DRIVE BY WIRE
Loci sent this:- Hi. I have a problem with my Volkswagen Polo 1.4 Tdi. It seems to have a good start but after I drive for around 35 minutes it loses the power so I could not pass 2000 giro. Thank you for your suggestions.

QUESTION? - DRIVE BY WIRE 
Anonymous asked:- My car is a polo 1.4 2012 model. When I start the car the EPC light switch on then I put gear to move the car but it limbs then I switch it off then start it again then the EPC light does not switch on then off I go... What could be wrong? 

ANSWER!
The trouble can be one of many things, among which are your accelerator pedal, throttle body, knock sensor, Fuel pump pressure, even a loose fuel cap. You need to check through each systematically but for that you at least need a scan of your vehicle.

ENGINE LIGHT COMES ON
Lee Kyprian left this:- Everyone who has ever owned a car has experienced the confusion and even panic which can arrive when your check engine light suddenly comes on.

QUESTION? VW ELECTRONIC POWER CONTROL
Abror Isoqov sent this:- Hello. My car is VW Golf 1.6 16v and I have a problem with acceleration it has no enough power. It accelerates very slow and at 5th gear it can get max 130 km/h. At neutral position when engine gets about 5000 rpm the EPC light comes on. After restarting the engine it goes off. Tester didn't determine any trouble codes. What can cause for this problem. I went about 7-8 auto services but any of them could help. But I didn't go to VW dealer because it will be very expensive. last time they charged me $125 just for diagnostic.  Please help me with this issue.   

ANSWER!
What you explaining is limp mode and everything else seems very odd. Because by the time the EPC light does go on, a DTC is already set which any scan tool should be able to retrieve. Unless there is a problem with you DLC wiring, so that communication between vehicle and scan tool is erroneous.

VW ERROR CODES
Steve Cain sent this:- Hi, vw polo 1.4tdi 2003, AMF engine code,  problem is that when driving at any speed, car looses all power, engine stuck on 1200 rpm, throttle pedal no response, glow plug heating light flashes, switch off & switch back on straight away, car drives normally, no warning lights. Can you shed any light on this problem, (driving my wife mad). Thanks, Steve 

ANSWER!
I have covered this problem quite substantially in previous blogs and it in your interest to ready through them.

WON'T REV
Anonymous sent this:- My VW Jetta 2002 1.8t stopped me on the highway and it refused to rev and the mechanic says it is the brain box. I don't understand is he correct?

ANSWER!
Yes he is correct, problem lies in the ECM circuit but not necessarily the ECM itself. Dude you need to get your car scanned to get a better idea of  the actual problem.

CAN-BUS
Hi! I read your blogs and saw writings from you  about the CAN bus protocol. I have a problem to understand something on my cars OBD connector and the CAN bus line. Can you please help me maybe? Can we talk about? When I connect my 2 channel  DSO to the OBD connector pin 6 and pin 14 ( CAN-H and L ) and pin 5 (GND) on my VW Polo 1.4D year 2003 I got this signal what I posted right now. But, when I do the same think on my Renault Clio 1.5DCI year 2003 I got the right CAN signal.  

ANSWER! 
The likely hood is that your VW Polo isn't CAN compliant because its still a 2003 and used KWP-1281 and KWP-2000 protocols.  All VW's after 2008 is fully CAN compliant.

ECM POWER RELAY OPEN CIRCUIT

ECM POWER RELAY OPEN CIRCUIT 

17069 - P0685 ERROR

Electrical problems seems to stymie everyone, but repairing an electrical fault can be fairy simple if traced logically. The above error relates to a relay. Relays are just remote switches. Audi, Volkswagen, Seat and Skoda relays can give a fair amount of trouble because its push-in spade terminals may corrode, or they may even pop out of the relay plate due to shaking on bumpy roads. Their contacts may overheat and fuse together, or the spring inside may snap or jump off. Its solenoid can even burn out. Or its plastic enclosure may melt and block the switch mechanism from moving. But these are not the only faults related to relays.

Question?

Will Wallace shared this: 
Hey, I am a bit desperate for advice here, so reaching out.  Having a problem with my GF's VW Polo 1.4L 16V (BUD Engine). I have had to jump start this vehicle every 4 days or so. It will run fine, and then after about 4 days won't start, it either makes a clicking sound (sounds like a relay and wont turn over) when trying to start or starts beeping with the Engine light showing and the Park Brake light flashing (and won't make any sound when turning key). 

Connecting up a scan tool brings up Error 17069. Looking around the forums it seems like quite a common fault, with no real definitive solution. The battery measures 12V without the key in and then goes down to 8.5v when  the key is in and ignition ready. I've tried disconnecting the Plus Battery terminal and connecting a Volt meter to it and the battery post + and setting the DMM to Amps but its not coming up with any amp draw which I think is good (Not sure if I am doing this correctly though). It seems like something is draining the battery or the alternator isn't  charging it properly? I had a battery test done at a auto store and they said  it was fine and the alternator was charging it properly which is bizarre. I have posted this as it seems like a common fault and would be good to get  some advice. Thanks in advance.

____________________________________________________________________

Answer!

Greetings  Will Wallace, so sorry to hear that you having so much grief with your Girlfriend's car. As much as I would like to help you, remote diagnosis without a full scan cannot always be accurate but I hope my thoughts on the matter may steer you in the right direction. The fact the you have  a scan with a 17069 manufacturer's specific code makes quite a difference. The generic code for this fault is P0685 and is relative to the  ECM Power Relay Control Circuit (See other codes below). From which  I can deduce that the Motronic ECM power supply relay itself  may be faulty, because of the 36-Open Circuit designator. However there are several possibilities. One possibility is that the solenoid winding is open circuit, and another is that its contacts doesn't close properly (open circuit), which is more likely. 

But there would also have been additional error codes, like 17072 or 17073. Considering either way, no rail voltage will reach the ECU, neither the injector coils, nor the injectors, etc, hence they won't function and the car would never start. So you need to prize-out the relay and do a physical check to make sure the contacts make or break as expected. The relay number is  J271 and will probably have the number 428 painted or stamped  on it. But before I explain how to do that, I want to raise a few points regarding the rest of your note. 

The clicking sound you hear, may or may not be the relay. If you said a single click I would agree that it's a relay, but since you said clicking, which implies several repeated clicks. It's most likely it's the starter solenoid that is chattering because their is insufficient voltage to keep it engaged, since you say it goes down to 8.5V under load. I'm inclined to favour this idea because it sounds like you battery is running down after 4 days and therefore not strong enough to drive the starter. But since you had that checked, try substituting another battery to make absolutely certain. 

The alternator could also be faulty and not charging the battery but I see you had that checked as well. Yet, it could imply that the diodes in the alternator are breaking down under load even though they function normal at idle. The battery voltage must be at least 11.5 volts constantly for everything to function as normal. Use your DMM and measure if there is any  resistance (ohms) between engine and body, there shouldn't be any. Also make sure you have a good connection  between the  negative battery terminal and the body. 

Regarding the amperage measurement, current is measured in series with the load. I don't think you should try to measure amps with your DMM because it may not be rated to measure more than 10 amps and may blow a fuse or damage its internals. Probably best to get a current clamp to measure current on cars. To return to the chattering, the starter could also have a intermittent power connection and could be the reason why it sometimes starts and sometimes not. Or the starter could be shorting to earth intermittently and draining the battery, hence the 8.5V. The best way to check this is to remove the starter and engergize it on a work bench to make certain it works the way it should. Before removing any control modules or relays from  the relay plate, make sure you disconnect the battery earth cable.

Relay J271 - Pin 85 and 86 are the solenoid terminal. Pin 85 is the 12V input whereas pin 86 is the solenoid earth. 
In the above image,  the only switch contact is between Pin 30 and Pin 87 which is normally open circuit.
When 12V is applied to 85  and 86, (normally happens when the ignition switch is turned  on) the relay 
should click and the power applied to pin 30 should exit on pin 87. If you hear the click but no voltage
 comes out  at pin 87, the relay internal contacts isn't making contact.
Try cleaning the contacts with fine sandpaper.

J271 varies from VW model to VW model, but once you have the relay out, check one of  its sides for the diagram of the pin-outs. It would look like the image on the bottom right.   The solenoid 12V supply will always be marked as 85, the negative always as 86, the normally open (N/O) contact as 87, or the normally closed (N/C) as 87a (if there is one). The pin marked 30 is always the switching voltage supply input. Notice that terminals of 87 and 30 are always larger than the other terminals because they carry a larger amount of current.  

Connect the relay solenoid to a battery with clip leads and measure the voltage at 87 and 87a, and verify that it switches over when you hear the relay click. Alternatively do a continuity test between pin 30 and 87, then again between 30 and 87a and make a note which one is open and which one is closed. Then connect power to the solenoid, pins 86 and 85 and verify that its continuity measurement switch over to the other pin. Unlike the image above, there may be even be more than 1 double pole double throw switch contacts on the relay depending on the model of your car. The Audi J271 is different to some VW's and has more terminals. It's also a good idea to check the relay socket wiring to or from the fuse box.  


P0685 - 17069   (ECM/PCM) Power Supply Relay - J271 - Circuit Open
P0686 - 17070  (ECM/PCM) Power Supply Relay - J271 - Short to Ground
P0687 - 17071   (ECM/PCM) Power Supply Relay - J271 - Signal to Positive

P0688 - 17072  (ECM/PCM) Power Supply Relay - J271 
Load Sensing Circuit - Open Circuit 

P0689 - 17073  (ECM/PCM) Power Supply Relay - J271 
Load Sensing Circuit - Short to Ground

P0690 - 17074  (ECM/PCM) Power Supply Relay - J271 
Load Sensing Circuit - Short to positive

P068A - (ECM/PCM) Power Relay Load Circuit - J271 - Opens Too Early  
P068B - ECM/PCM) Power Relay Load Circuit - J271 - De-activated Too Late