audittis

Hello,

During the recent very cold days, I tried to start my Audi TT (Turbo 1.8L 5 Speed Manual Transmission) parked in the garage. It cranked for about 10 seconds, it didn't start, but then it stopped cranking. Any subsequent attempt results in NO CRANK.

After charging the battery - new, a few months old - the NO CRANK condition continues.

So, I've started a research of the possible cause. I expect this to be a slow step by step work, as I have not done this before on this car, I am not familiar enough with the internals of the car, nor with the Bentley Documentation. I am also very careful, to avoid creating any further problems, and in the same time I am going to take notes, as it is going to be a learning process as well.

First thing can be noticed is the following:

When switching the Ignition Key ON, the following lights on the Instrument Panel are ON,- EPC, Long Beam Headlights, Anti-Slip Regulation (Left) , Emergency Flasher (Center) , Check Engine, Air Bag, ABS, BRAKE, Battery, Seat Belt lights (Right) and OK text in Center.

after a few seconds, one by one the following lights go OFF:

- Long Beam Headlights, Anti-Slip Regulation (Left) , Emergency Flasher (Center) , Air Bag, ABS, BRAKE, and OK text in Center.

So the lights that remain ON are: EPC (Left), Check Engine, Battery, Seat Belt lights (Right).

There is NO Error/Warning code/symbol in the place of the OK text that went blank.

I have not paid attention enough to memorize the normal sequence, so at this point I am not sure if this is a Normal behavior, or it is an indication of something malfunctioning.

Further, I've performed the following actions and/or checks:
1. with the Solenoid wire disconnected, I've connected a 12V Check Light Bulb between the Solenoid Wire Plug, and Negative Pole on Battery. The 12V Check Light Bulb stays OFF, when attempting the start/crank, which indicates that in the chain of elements between the Solenoid Socket/plug and Ignition Key, something is not closing the circuit/working:
Went further and
2. checked fuses #10, #29, #34 (engine timing), #6, #14, #38 (central locking system) - all good
3. checked the "Starting Interlock Relay" - J207 on Bentley CD wiring diagram - all good - Switch goes Close, when applying 12V on Solenoid tabs
4. checked the Clutch Pedal Position (CPP) switch - F194 on Bentley CD wiring diagram - all good - Open when Clutch in Normal, Closed/Short when Clutch activated/pushed to the floor.
5. checked Solenoid and Starter - Solenoid engages and Starter cranks when 12V applied to terminal #50 on Solenoid - 50 on Bentley CD wiring diagram

So, my next step is to check the Central Locking System J429 on Bentley CD Wiring Diagram. I am thinking that I could try to bypass the Locking System, by connecting directly Locking System 3/3 and 3/4 terminals, connected to the J207 Relay, respectively F194 CPP. If No Crank condition continues, next would be to check the Ignition Switch.

As the car doesn't not seem to have an Immobilizer - There is no Key Light on the Instrument panel, and no documentation in the Audi TT User Manual - I don't see the purpose of the Central Locking System being part of the circuit.

Thank you in advance of any helping suggestions.

Mister Bally

Run a diagnostic scan using the Ross-Tech software and interface. Buy it from them if you don't have it. Otherwise, you are wasting your time and money. Or, take the car (tow/trailer if necessary) to someone who has the diagnostic equipment.

audittis

Thank you for reading my post and making a suggestion. It seems to be very useful to own a ob board diagnostics soft/hardware tool.

I've ran a diagnostics, just in case.

It showed NO Error Codes stored, and ALL supported on board tests completed. So, it seems that as far as the tool's ability to provide diagnosis info, things seemed to be fine.

audittis

Today, I've continued the analysis/work, from where I left it before my thread opener post.

I've reversed the order of "next things to do", as it made more sense logically to check the Ignition/Starter Switch and Key Assembly first, and go to the Central Locking Control last. So I've went for testing if the Ignition Switch provides 12V+ to the Starter Relay (J207 on Bentley wiring diagram.

First I had to determine the Starter Relay socket connecting terminals - (2), (4), (6), and (8) on the Bentley Wiring Diagram.

With the Relay removed from its socket, from the Back of Relay (Bitron 204, 12V.40A) connector numbers, and the painted electrical diagram on the side of the Relay, I could do that determination.

Just to make sure, I've done a visual check of the wire colors, using a mirror. In the mirror I could see behind the Relay Panel, the wires to the 4 Relay Socket terminals.
Colors checked against colors indicated by Bentley Wiring Diagram.
And then I've checked electrically, as the terminals (4) and (2) seem to be connected, according to the Bentley Wiring Diagram (#4). Ultimately, this particular connection between (2) and (4) seems to be a trouble maker - will post more info on that later. The two (4) and (2) terminals are where the 12V Positive voltage should appear, when the Ignition Key is switched to "Starter Cranking" Position.

To my surprise, the voltage read with a VoltMeter on terminal ((4) and 2) with the Key in the Crank position was 0V (zero volts).

So, THIS IS IT!!!

The Ignition Key Switch (terminal 50b on Bentley Wiring Diagram) does not provide the 12V to terminal (4) and (2) of the Starter Relay (J207), when the Ignition Key is in "Starter Cranking" position.

I could not find any documenting of a Fuse that would control this particular voltage - either in the Audi TT User Manual, or the Bentley Wiring documentation - so, the problem must be at the Ignition Key Switch.

The cranking during the cold day, which has started this problem, must have damaged (possibly overheating) the 50b terminal and/or connecting wire at the Ignition Key switch terminal, or damaged internally the switch.

I don't think I've cranked more than 10 seconds, which is what the User Manual suggests, nevertheless, that's what seems to be the problem.

audittis

To make sure that there is no additional cause besides the Ignition Key Switch not providing the 12V+ to the Starter Relay (J207), I've decided to test further, to see if I can trigger a Crank sequence by applying 12V to the Starter's Relay socket terminal (8) - which is connected to the Starter Solenoid.

I could have done this with the Ignition Key in OFF position, in which case there would be only Starter Cranking... or with the Ignition Key in ON position, in which case, the engine could start and run.
I've opted for the latter.

So, I've used a pre-soldered "flat pin" to a 2.5 wire, which I've inserted in terminal (8) of the Starter Relay socket, and with the Ignition Key in ON position, I've touched the other end of the wire to the Nut/Lug Marked #30 on the Relays Back Panel, which provides the12V+ (Bentley Wiring Diagram shows Battery Positive 12V at terminal 30).

And.... the Starter Cranked, and the Engine STARTED. Applause....

I've let the engine run for a few minutes, and then switched OFF, and start again a few times, by using the same procedure. Every time, the Engine started just fine. .....

So that's the cause.....the Ignition Key Switch, or the wiring between terminal (2) of the Starter Relay and terminal (50b) on that Ignition Switch are the problem.

As a solution to the problem, normally the next step would be to get to the Ignition Switch and see what the problem is - fix the wire, if it is damaged, or replace the switch if it is internally damaged.

Another option is to install a mechanism that would bypass the Ignition Key Switch Start Cranking Position - for instance installing a ENGINE PUSH START Switch.

In principle, using a PUSH START Button would require the presence of the Ignition Key, and the Ignition Key in the ON position, and thus seemingly as secure/anti-theft, as when such a Push Start button is factory installed.

The latter solution is quite appealing, as it seems less or comparable work amount with removing/reassembling the steering wheel and AirBag, the steering column switches, and the Ignition Key Switch socket, which all together seem quite complex/laborious... At this point, I have a suspicion that it is the overheating of the circuit that caused the problem, so this approach removes the overheating risk.

A third option would be sort of a combination of the first two:
a. replace the defective Ignition Key Switch, or fix the wiring to terminal 50b of the Switch. Keep connection of Relay's activation terminal (4) to the terminal 50b of the Ignition Key Switch.
b. move the Relay's Switch terminal (2) from terminal 50b, on the Ignition Key Switch, to a 12V+ terminal, through a Fuse. Ideally would be to use one of the "unused" Fuse slots in the Fuse Panel. Appropriate Fuse amperage can be determined by measuring typical current through the Relay Switch.

Mister Bally

Good troubleshooting techniques you used once the diagnostic scan proved to not help you.

Only hitch I see with a "push to start" button is that you would be able to crank the engine with the car in gear. This could be a safety hazard. That said, if you are smart enough to figure out this problem, you are smart enough to never crank the car while the transmission is engaged.

Not sure if you have an auto or manual. If auto, there is a park switch and with a stick, a clutch pedal switch. Perhaps one of those could the your issue here....

audittis

Thank you for your reading my posts and commenting.

Indeed, the accidental touching of the start button while the engine is running is an important concern.

As you've implied, the Clutch Pedal Positioning (CPP) Switch is significantly helpful. My car has a Manual 5 Speed Transmission so the CPP switch would require the clutch to be activated/engaged, and thus eliminate the danger of the car moving when accidentally pushing the Starter Switch while the Ignition Key is ON. An accidental push and triggering a crank during engine running and damaging teeth on the starter drive gear, or flywheel ring teeth is protected against by the starter's sprag clutch.

As at a second thought, just to prevent possible future problems, I may end up opening up the steering column just to see the extent and fix the damage to the Ignition Key Switch, if it presents risks..

In this case, I may go with the 3rd option, which is besides fixing the Ignition Key Switch also changing the powering of the Starter Relay's Switch from the Ignition Key Switch* to a Fused Battery 12V+ point, and thus eliminating the danger of damaging the Ignition Key Switch..

* A thermal protection of some sort of the Ignition Key Switch would have probably prevented the problem.

audittis

so....as the analysis/diagnostics work so far pointed in the direction of the Ignition Switch, I've taken the next steps:
- before moving onto the Ignition Switch, I've made sure that all wires behind the Relay Panel are OK,

To achieve that I've removed completely the bottom dash cover in order to get an easier access to the the under dash board area.

For that, I've disconnected and removed the headlights switch assembly, and removed the ODBII socket/outlet. I've reconnected back the headlight switch, so that from an electrical perspective everything is in place. I've removed the two bolt/nuts that hold the two piece Relay Panel in place. Tilted the Relay Panel so I could see the wires behind. Went a step further, and removed the Starter Relay connector socket from its place/slot in the Relay Panel, for even a better visual access to the wires at its back.

All wires looked OK,

I could see very clearly the wire from terminal (4) to terminal (2), which is where 12V+ should be seen, when the Ignition Key is moved to the CRANK position.
Before moving to the next step, I've reinstalled the Starter Relay socket in its slot on the Relay Panel, and then the Relay Panel back in its place, securing the bold/nuts in their original position.

Next step:

audittis

So... the next step was to open up the steering column to get access to the Ignition Switch:

a. - removed the Steering Wheel Air Bag - following the Bentley Manual - by removing the two holding screws, and then disconnecting it from the steering wheel harness. Before disconnecting, touched the battery + and b. - wires and ground to discharge/neutralize any static electricity in the system.
c. - removed the Steering Wheel - following the Bentley Manual. Made sure that before removing, there is a marking of the position.
d. - remove the top cover of the steering column - two holding long screws with heads at the bottom cover. I tried to remove this before the Air Bag and Steering Wheel, but there was not enough room for it.
e. - remove the bottom cover of the steering column - one screw on the bottom, and two small screws on the front side.
f. - remove the handle of the Steering Column tilt/position lock, so that I could completely remove the steering column bottom cover.

I didn't need to go any further, as I had full access to the Ignition Switch connector, and the switch itself. All components looked fine, with NO heat damage.

1. - removed the Ignition Switch connector plate - all wires looked OK - no heat damage.
2. - tested the wire between terminal (2) at the Starter Relay and Terminal (50b) at the Ignition Switch contact plate. Wire OK. Great!
3. - tested the wire between terminals (30) - actually there are two , which I am going to call 30a and 30b - and the 12V+ lug/nut at the Relay Panel. Wires OK. Great!

The Ignition Switch looked fine, NO heat damage. Next step was to test the Ignition Switch while in its place:

i. - first tested the connection between terminal 30a and 30b - they are NOT connected inside the switch. Further electrical testing indicated that each of the two, provides the 12V+ to different terminals on the Ignition Switch, as follows:
- 30a provides 12V+ to terminal 50 and 75
- 30b provides 12V+ to terminal P, 50b, 15 and 86s
ii. tested for "contact/short" between terminal 30a and 50 - contact is a YES, so this works fine. Terminal 50 provides 12V+ to the Fuel Pump Relay
iii. tested for "contact/short" between terminal 30b and 50b - contact is a NO, so this DOES NOT WORK. Terminal 50b provide 12V+ to the Starter Relay.

Next step was to remove the Ignition Switch. Loosen the two screws holding the switch in its place, after first removing the locking paint on the screw heads. The Ignition
Switch came out very easily.
So, next step was to test the Ignition Switch out of its place.

I. tested for "contact/short" between terminal 30b and 50b - contact is YES, when the switch is turned far into the CRANK position. Hm..... That seems great!, the switch is working after all.

So, I've put the Ignition Switch back into its place, and tested again, repeating step (iii).

- result is NO "contact/short" between 30b and 50b - what a disappointment !!!!!

It seems that when in its place, in its housing, and secured with the two screws, the Ignition Switch turning to the CRANK position, does not go far enough in terms of angle, to make the contact between terminal 30b and 50b.

So, I've ordered a new Ignition Switch, just to make sure. It will arrive in two days.

Meanwhile I could not stop thinking that the behavior opens up a new possible cause, besides the Ignition Switch, which is "something" that limits the rotation of the Ignition Key, and the Switch Actuator to less than the need rotational angle?

Note: I forgot to mention earlier, that the Key has a good battery in it, and the Remote Lock/Unlock of the doors and trunk lead work, in other words the components for Remote control from the Key work.

audittis

While waiting for a New Ignition Switch, I've performed a few more operations:

1. visually check the Ignition Switch housing, and the Ignition Switch Rotational Actuator. Visually it seems OK.
The Actuator can be inserted into the Switch only in one position, so a miss insertion is being excluded.
The Actuator is cast metal, which is by its nature very rigid, so I am excluding the possibility of the Actuator being slightly twisted, as well.
2. checked the rotational angle of the Key and Ignition Switch Rotational Actuator . I cannot tell precisely, there is an approximate 110 degree rotation of the Key and Switch Actuator. This does not seem to be enough for the switch.

So, the question in my mind is: "is it possible that there is an intended mechanism that is reducing the rotational angle of the Actuator? " or is the current rotational angle reduced by some internal damage or age?

Meanwhile, I've performed two more steps:
a. opened the Ignition Switch, and cleaned the terminal 50b sub-switch with very fine grit sandpaper - gradually from 600 to 1000, to 1500 to 2000 to 3000. That didn't resolve the problem.
b. swapped the Ignition Switch P sub-switch with the 50b sub-switch - the P sub-switch is unused, and so it is like new. That didn't resolve the problem either.

So, at this point it seems that the 30b to 50b sub-switch inside the Ignition Switch seems to be excluded as possible cause of the problem.

Would it be possible that the Plastic Cam that activates the sub-switches inside the Ignition Switch has changed its shape? Visually, everything looks OK, so I can't tell.

Important is to note that I DID NOT find any heat damage - melt wire insulation, or melt plastic, or melt wires, as originally I assumed I would find.

At this point, need to WAIT for the New Ignition Switch to see if the problem is the Switch. If it is not, then the problem is further in the Ignition Key and Actuator assembly.