ABS FIX

1 First of all, we needed to find out which ABS unit was fitted to our Golf. You’ll need a torch to read the numbers and letters on the side of the ABS pump. Ours is an AF pump – you can just about see the ‘A’ here.

2 This was our main problem: the permanently-illuminated traction control light. Parkside Garage in Worksop scanned the system with Autologic and Snap-on, coming up with the same fault code: ‘1435 sensor 1 for brake booster G201’.

3 The first task when replacing the ABS block is to disconnect the battery earth and then unplug the MAF or air mass meter wiring plug – the MAF is part of a primary inlet system in the top engine cover. Unplugging it with the battery connected means you may get an EML light.

4 You can see the MAF at top left (circled) and the air intake at bottom right (circled). There are two metal spring clips securing the MAF to the inlet manifold, so these need to be carefully sprung off with a small flat-blade screwdriver before the engine cover lifts off.

5 On all Golfs and Jettas, the battery sits on the passenger side of the engine bay. It’s virtually impossible to get to the ABS block with it fitted, but that’s not a problem – both it and the plastic tray on which it sits are easily removed. You’ll need to reset the clock afterwards.

6 Here’s the ABS block in more detail. The plastic body of the ECU is positioned so you cannot read the numbers from the side, but only one type of ECU is fitted to the Af-type pump, so that’s not an issue. Note that there are a couple of braided flexi-pipes to undo.

7 The first thing we’re going to do is unplug the ECU electrical plug, and attach it to our replacement ABS unit to see if it will communicate with our diagnostics. This is simple enough as the plug can be accessed with the battery still fitted – just lift this locking tab upwards.

8 Inspect the plug carefully for any corrosion in the pins. These plugs rarely suffer, but if any damp has got in there then green mould will follow. If you find any, spray electrical contact cleaner in there, then remove/refit the plug a few times to clean it up.

9 Our plug was in perfect condition, so we carried on and inserted it into our replacement ABS unit. Despite being from a SEAT Leon diesel, it had the same part numbers as our Golf GTI unit and we thought it would work. However, VW doesn’t make it that easy…

10 Jez at Parkside Garage interrogated the new unit with Autologic and, at first, it looked as if the SEAT ABS block could be coded to our car. If it worked, it would be the cheapest ABS fault repair ever – almost cost-free once we’d sold our spare ABS unit on ebay.

11 With that encouraging sign, it was time to whip out the battery and swap the ABS block. Remove the negative terminal first, followed by the positive terminal, then undo the clamp bolt as shown. The battery can then be lifted out.

12 The battery tray is even easier to remove, as long as the retaining bolts aren’t rusty. Our 2007 car is remarkably clean, so the bolts came out without tears. On reassembly, don’t forget to add a bit of copper grease or similar to the threads.

13 The ABS block was now exposed and ready to come out. Use a selection of tight-fitting 10mm, 11mm and 12mm spanners – those special brake pipe spanners are even better. Place an old towel under the unit to catch brake fluid drips and take care not to bend the solid pipes.

14 Here is the ABS block with all of the pipes unscrewed. The unit is not bolted, just pressed into tight-fitting rubber bungs in the body, so it lifts out with a sharp yank. Feed the unit out past the pipes – these have very fine threads, needing extreme care when refitting.

15 Here’s our £17 replacement ABS block. As you can see it has an antitamper white sticker on the ECU reading ‘do not remove’, indicating that it is a reconditioned unit – it would have been a result had it actually worked on our car. You can also see the rubber bungs.

16 These are the numbers on the side of all of our ABS ECUS. The ‘ESP’ is a giveaway as only Golf 2.0 FSI and GTIS, as well as some SEATS and Jetta/ Touran models, had this. Regular Golfs such as the 2.0 TDI and 1.4/1.6 FSI models have a different ABS unit.

17 The replacement ABS block was fitted and the system bled as shown. On our car, the front bleed nipple came undone easily, one rear caliper was new and the other rear was a bit touch and go. but it released with a bit of effort and the brakes were pressure-bled easily.

18 This is where everything started going wrong. Despite our best efforts, the replacement ABS unit would not code to the car. The steering angle sensor is set by driving it in a straight line, but even with that done, the replacement unit didn’t want to know.

19 Now we had this Christmas tree selection of warning lights, as well as an infuriating high-frequency beeping from the dash. There was no way the GTI could drive around in this condition, so we went straight to ECU Testing in Heanor. Could they fix it?

20 Upon arrival, Roger Bagg, founder of ECU Testing, used a laptop to check if our replacement ECU could be coded to the car whilst fitted. Not a chance, although it would be possible on a bench. So a skilled technician replaced the faulty alloy valve block on our original unit.

21 This is a £250 rebuilt unit from ECU Testing – that’s a quarter of the £1000+ that Volkswagen would charge for a new one, which would be uneconomical on a Golf of this age. It’s rare that a faulty unit can’t be repaired – ECU Testing have very good stocks of refurbished units ready to go.

22 ECU Testing is a highly professional and very impressive set-up that turns over hundreds of ECUS every day. They also repair and sell VW DSG ECUS and engine ECUS for a huge variety of makes and models.