Honda Pan-European ST1100AY  
Honda Pan European ST1100AY
ABS Fault Finding.

ABS

The ABS is brilliant - it works. It gives a pulsing sensation through the brake levers - which first time you use it, you think "What the hell ......" - but the wheels do not lock and you stay upright.

TCS

This works too - but in a much more dramatic way. Apparently, the ignition is retarded if one wheel is recognised as going round faster than the other. It doesn't feel like this. It feels as though all power has been cut to the engine, and rather sickeningly you tend to lurch forward to meet the wind screen. Sickening because at the time that this happened to me, I was in mid-overtake, accelerating hard. In fact the roads were dry, and the front wheel was planted on the ground. The TCS kicked in because a fault had developed on the rear sensor, and it cut the engine for much longer than it would normally be out of action. Made me wonder which would be worse when I hit a diesel patch - the extra speed on the rear wheel, or the sudden drag of the engine. But this isn't fair - as soon as the wheels started revolving at the same speed again, all would return to normal. Mine didnt because the sensor was broken.

New Information - Added June 2007

Service brakes - ie added new pads front and rear. I did what I normally do to aid re-installation - push the pistons back into the body. Of course, I forgot that I had recently flushed the old brake fluid out and filled up with new, so there wasn't the space to push the fluid back into the system that there normally is.

I didn't think much about it, until I started the bike - the flight deck was like the starship enterprise - flashing lights all over the place. Mainly the ABS / TCS lights. I couldn't find a fault code, the lights just kept flashing. The sequence below didn't work, although the bike was fine to drive - just no ABS. Then I realised that the normal whirr of the ABS pulse motor hadn't happened when I turned on.

Opening up the brake fluid reservoir, it spilled fluid over the tank, so I got the tubes out and relieved the pressure in the system at the bleed nipples. No joy, but on checking the fuses, discovered that the ABS fuse had blown - presumably because the motor for the ABS system couldn't pump the fluid around.

Replaced the 10A fuse. Perfect again.

The Original Problem

ABS and TCS warning lights would not go out.

Prior to this, TCS had been cutting in intermittently and in the last day of the problem was preventing the bike from running at all - except at very low revs, crawling along in the gutter ! Turning TCS off cured this. The problem fault code revealed that the rear sensor was at fault. I cleared the code from memory, expecting the code to reappear - but no fault codes were ever stored in the ECU after this.

My intention was to purchase a new sensor - but decided to leave the solution to the experts when I discovered that a new sensor costs £199. The local dealer charged me £235 for 5 hours of fault finding work - but they were unable to find the fault in this time. I asked them not to continue. They had followed the flowchart in the manual, which didn't cater for the problem that I was having. Looking at www.st1100.org reveals that other Pan owners have had a similar experiences. ie - Honda specialists being stumped when they do not find a fault code to work on. The official Honda manual doesn't help in the circumstances that I describe here. The local dealer lent me the official manuals to work with myself. These notes have been put together from the official information, and the information that I have found out by puzzling things out for myself.


If there is a fault in the ABS system, the Electronic Control Unit (ECU) will store the appropriate fault code in its memory. In fact it stores the last two fault codes.

You can find out what the fault is by following the procedure described below.


To recover the fault code:

Turn ignition off

 

Hold down the ABS/TCS indicator light switch below the left hand fairing pocket

 

Turn on the ignition while keeping the switch held down and watch the ABS warning light on the dash.

Note that the warning light has a wider lens beneath which are two bulbs. In my case, the left hand bulb lights at this point, the right hand bulb remains off.

After about 5 seconds, the warning light goes off. At this point (within 1 second), release the warning light switch. The ABS warning light should begin to flash.

The flashes consist of one long flash, followed by a number of short flashes. Count the number of short flashes.

Do not press the warning light switch again, unless you wish to clear the problem codes. Instead, turn the ignition off. This leaves the same problem codes in memory

Note that the system will cycle through two sequences and then repeat.

eg (using FLASH to indicate a long flash)

FLASH flash flash flash flash
FLASH flash flash
FLASH flash flash flash flash
FLASH flash flash

Indicates that the two fault codes are 4 (the most recent fault) and 2 (the previous fault).

To clear the fault codes:

Follow the procedure above to retrieve the problem codes.

 

Press the ABS / TCS indicator light switch while the indicator light is flashing.

 

 

In my case (different from the info given in the official Honda workshop manual), both ABS lights illuminated at this point. It seems that when the system is in fault diagnosis mode, only the left bulb of the two is lit.

What the Fault Codes Mean:

Code

Description

1

Faulty front modulator crank angle sensor system

2

Faulty rear modulator crank angle sensor system

3

Faulty front modulator control motor system

4

Faulty rear modulator control motor system

5

Faulty front wheel speed sensor system

6

Faulty rear wheel speed sensor system

7

Faulty power circuit

8

Faulty ABS control unit (ECU)

What the Manuals Don't Tell You - (things I've discovered for myself)

Fault

Comment

The ECU will record a fault if the sensors stop working during the course of riding.

ie - they have been working, but then they stop working - so a fault is recorded. However, if it is a faulty sensor, the system will never store the same code again.

Note that the same error code is stored if after arming itself, the system detects that one wheel is rotating faster than the other (eg wheelies, very bumpy ground, putting bike on centrestand)

The ECU will not record a fault if one or both sensors is not working when you start out.

My experience is that the ABS and TCS warning lights come on and stay on when one sensor isn't working. Because the system hasn't armed itself by verifying that both wheels are turning at the same speed, it cannot check if the sensors are working or not. One faulty sensor, or problem with the connectors / wiring loom will cause this to happen, and there will be no fault code stored in the ECU. So - if you get a faulty sensor, you will never see the error code again after the code has been cleared from memory.

So - without an error code, how do you check if a sensor is faulty ?

Before doing this, make sure that you have recorded the 1 or 2 codes that have been stored - because you are about to clear them from memory !

  • Try to retrieve the problem code as before (yes I know you've done it already. Do it again).

  • Clear the problem code (yes - even if there wasn't a fault recorded)
  • Do NOT turn the ignition off.

At this point the lights look just like they are when you turn the ignition on - but this is not the case. Only if you have gone through the above procedure can the following test be carried out.

  • Spin the wheel as fast as you can and watch the ABS warning light. If it flashes, the sensor is working. (nb - you will need a mirror or a friend to check this for the front wheel - the light only flashes while the wheel is in motion. The back wheel is easy, you can start the engine and slip it into gear)

Sensor or Wiring ?

The two sensors are interchangeable. Remove the front one, put it on the back and vice versa. If the problem stays on the same wheel, the fault is in the wiring or the ECU. If it moves with the sensor, the problem is in the sensor or connector.

You need to remove various bits of fairing to get at the connector for the front sensor. It might be possible by removing just the clear screen and the plastic bits that cover the rear of the instruments - but I've not tried this.

Removing the sensors.

The rear one is easy. The connector is the yellow, 3 pin connector on the right of the machine, alongside the petrol tank. The front sensor connector is attached to the fairing stay on the right of the bike behind the headlights - near the ABS modulator and radiator filling cap. The front sensor cable is attached at various points with fiendish cable clips, and these have to be undone. Don't use force, the clips have a pivot to allow movement when the steering is turned. There is a knack to undoing them. I wish I had it ! The front sensor itself is held on with one allen bolt, behing the front fork. It then slides off a pin without having to detach the brake bolts.

Other observation.

At one point, I could not get the yellow TCS lights to go off. Even by turning off the TCS at the switch. My heart sank, because it suggested an ECU fault to me. However, I unplugged everything to check for corrosion, and plugged it all back again. It was after unplugging the black 16 pin and white 16 pin connectors from the ECU, waiting a while and plugging them in again, that this behaviour stopped. ie - the yellow ECU lights worked normally. It occurred to me that the ECU computer might have 'crashed', and this procedure restored it - but I don't know.

Electronic Control Unit.

If, like me, you are doubtful about the reliability of such electronic equipment in the harsh environment of a motorbike, and are suspicious of electrical faults rearing their heads after much winter riding on salty roads - then you'll be wanting to take the ECU off and having a look.

Don't bother. Inside the plastic case is a metal case, with drain holes. Inside the metal case, the electrical circuitry is 'drowned' in what looks like an epoxy resin overcoat. There is no way that salt or water is going to penetrate that.

A final ponder.

What if my TCS switch hadn't worked ?

When the bike was crawling along at less than walking pace - the ECU thought that one wheel was going faster than the other and consequently cut the power. The situation never sorted itself, so power was never restored to the wheels. If for some reason the TCS switch didn't work to get me going again - how long would I have spent trying to track the fault in the ignition system ?

I hope that this information helps anyone in tracking down the problems that I have had with this. The fix in the end came by purchasing a sensor from a breaker's yard for £10.

 

These pages relate to a bike which I owned, rode and serviced from when I bought it at 19,300 miles to when I sold it at 70,100 miles. The pages were intended to provide information to a prospective buyer, but are maintained here as information for anyone who may be interested.

Website 2011 JFHeath