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Discussion Starter #1 (Edited)
In the last part of the 1.9TDi wiring write-up I covered stripping the unnecessary wiring from the main harness and identifying the connectors etc. which need to be retained for the cabin end of the harness/loom. This time I'm going to list the stuff you should be left with at the other end of the harness i.e. under the bonnet. The pic below shows what you should be left with having removed all of the redundant wiring. As mentioned previously, I have covered all of the connectors in section A below in part 1. The remainder are

B (EGR/MAF/N75)
C (ECU)
D (Engine/Crank sensor/oil pressure/Injector pump/etc.)




So what connectors should I be left with on the engine side of the firewall?

Well as I have a Golf 3 (1997) harness, this is what I found (other vehicles will be similar if not identical). The ECU connector(s) styles may differ if you have a later donor vehicle. The one I have is a Bosch 68 pin ECU so has a single connector later ones have 2 separate connectors. Below is an illustration of the connectors (numbered 1-9) from 'C' & 'D' above at the far end of the harness you should be left with:




1) Engine Multiplug
Numerous items connected here incl. glowplugs, temperature sensors, oil pressure sensors, etc. I won't cover all of the individually connected items as this connector is large and it's purpose is fairly obvious.

2) Inlet Temperature Sensor
Black two pin connector
Pin1 = brown/blue -> analogue ground -> pin33 ECU
Pin2 = blue/yelow -> pin64 ECU

This signal is used by the ECU to determine the temperature of the aircharge entering the engine from the intercooler and is used to adjust fuelling and control other engine parameters.

3) Injector Pump Connector

Black eight pin connector (only pins 1-7 are used)
Pin1 = purple/black -> modulating piston movement sensor -> pin29 ECU
Pin2 = grey/green -> modulating piston movement sensor -> pin7 ECU
Pin3 = white/green -> modulating piston movement sensor -> pin52 ECU
Pin4 = brown/blue -> analogue ground -> pin33 ECU
Pin5 = black/yellow -> pin 23 ECU (ECU sensor supply)
Pin6 = brown/yellow -> metering adjuster -> pin49 ECU
Pin7 = yellow/black -> fuel temperature sensor -> pin63 ECU

This connector handles the fuelling and injection timing adjustments as well as the fuel temp. measurement.

4) Alternator Field Coils
Note that this should be connected to a 2 pin connector that fits the alternator, as I didn't remove the loom from my donor vehicle the person who did cut the connector off in error. Suffice to say that this should be connected to D+ on the alternator itself. The wire is plain blue and is connected to pin 3 of fusebox connector 'F' as shown below.




5) Starter Solenoid
Black single pin connector
Pin1 = red/black -> starter solenoid -> pin1 connector 'F' fusebox

This is the main switched supply to the starter solenoid and is carried from the ignition switch through the fusebox to pin1 of connector 'F'

6) Reverse Light Switch
Black two pin connector
Pin1 = black/blue -> (switched side) reversing lights -> pin7 connector 'F'
Pin2 = black/red -> +12V supply - terminal 15 via fuse S14 (10A) -> pin6 connector 'F'

Self explanatory I think.

7) ECU 68 Pin Connector
Black 68 pin locking connector
Not going to list all 68 of these but will include them later as a list for people to use if required

8) Crank Position/speed Sensor
Black three pin connector
Pin1 = black -> analogue ground -> pin33 ECU
Pin2 = blue -> crank speed sensor i/p -> pin8 ECU
Pin3 = grey -> battery ground -> pin1 ECU

This signal is used by the ECU to determine the crank speed and position. This has a direct bearing on injection timing/quantity and a number of other parameters.

9) Needle Lift Sensor
Brown two pin connector
Pin1 = grey -> pin12 ECU
pin2 = blue -> pin11 ECU

This sensor is used to calculate the actual point of commencement of fuel injection from the time difference between the signal of the needle lift and the TDC signal supplied by the crank speed/position sensor. At the same time, the ECU compares the actual point of commencement of injection with the setpoint stored in the control map and corrects any deviations from that setpoint.

At the other end of the harness and adjacent to the fusebox connectors are three other connectors shown below:



1) Boost Control Valve (N75)
Black two pin connector
Pin1 = black/yellow -> sensor supply +12V (terminal 15) -> pin23 ECU
Pin2 = red/blue -> pin47 ECU

This signal is used by the ECU to regulate boost depending on engine speed, throttle position, and other engine parameters.

2) Mass Airflow Sensor MAF
Black six pin connector (pin 4 unused)
Pin1 = red/green -> pin19 ECU
Pin2 = brown/blue -> analogue ground pin33 ECU
Pin3 = black/yellow -> sensor supply +12V (terminal 15) d -> pin24 ECU
Pin4 = N/C
Pin5 = brown -> pin23 ECU
Pin6 = brown/red -> pin13 ECU

This signal is used to measure the airflow entering the inlet. Fuel and injection timing etc. are then adjusted accordingly

2)EGR Control Solenoid (N18)
Black two pin connector
Pin1 = black/yellow -> sensor supply +12V (terminal 15) -> pin23 ECU
Pin2 = brown/white -> pin25 ECU

This signal is used by the ECU to regulate the EGR phase when the motor is at low/idle engine speeds. It is driven by a PWM signal whose duty cycle is varied depending on a number of atmospheric (baro pressure etc.)/engine conditions.

So do I need to make any other modifications to my wiring harness?


In the old engine harness you removed from the van, there is a pair of wires which are connected to the instrument cluster via a two pin inline connector on one end and the header coolant level sensor at the other. They look like this:



and these are the connectors (top = fusebox end, bottom = coolant header tank end):

.

You need to slice the tape open on the old engine harness and remove this part. Once you have done this, remove the bit shown above, attach it to the new TDI harness and re-connect at both ends.


A useful tip also is not to tape the stripped out TDI harness-up until you have figured out how it is routed around the T4 engine bay, when you are happy then get to work with the tape. This will allow you to take all the curves/bends in the harness in account and make the routing neater when applying your choice of tape - I used self-amalgamating tape but ordinary insulation tape is fine also.

And that's it. I welcome any information which I can use to add further detail to this guide in the form of circuit diagrams for other vehicles/ECUs so that it will in time develop into a more comprehensive source of info. Happy tdi'ing

Additional ECU pin out info:

1.9TDI 68-Pin ECU Pinout (p/ns: 028 906 02X xx)

Copied from a 1997 Golf TDI diagram – note: all pins are included below, but not necessarily used


No code has to be inserted here.


No code has to be inserted here.
 

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Re: 1.9TDI Wiring -Part 2 Engine

Just a quick addition to make to this thread. With regards to the water circulation run on pump; the wiring for it is part of the radiator fan curcuit and it connects the same as it came out. When i was doing mine i was unsure of weather it would work but nothing is disconnected so technicly it should T:
 

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Discussion Starter #4
Re: 1.9TDI Wiring -Part 2 Engine

Just a quick addition to make to this thread. With regards to the water circulation run on pump; the wiring for it is part of the radiator fan curcuit and it connects the same as it came out. When i was doing mine i was unsure of weather it would work but nothing is disconnected so technically it should T:
The harness for the pump will remain on some vans only. If you have a 2.4D, the electric pump wiring is part of the original engine harness.
 

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Re: 1.9TDI Wiring -Part 2 Engine

Guys I need a little leg-up please.......

Removing the loom from the van - i've tracked the loom back into the fusebox and I assume plugs (F), (G1), (G2) need to be replaced with the TDi donor versions.......

I also assume this applies to all the other wiring including the glowplug supply.

Below is one of the (G) plugs......G2 i think....
The two wires arrowed do not head out under the bonnet but instead loop back to the fusebox and connect to the black box on top of the fusebox arrowed in the second piccy.





The question is.............are these required and if so, what the fark do i need to do with them LOL:

MTIA
 

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Discussion Starter #6
Re: 1.9TDI Wiring -Part 2 Engine

Guys I need a little leg-up please.......

Removing the loom from the van - i've tracked the loom back into the fusebox and I assume plugs (F), (G1), (G2) need to be replaced with the TDi donor versions...
Yes - just plug the old engine harness and any associated stuff out and throw away. Plug in your new TDI harness

I also assume this applies to all the other wiring including the glowplug supply.
Yes

Below is one of the (G) plugs......G2 i think....
The two wires arrowed do not head out under the bonnet but instead loop back to the fusebox and connect to the black box on top of the fusebox arrowed in the second piccy.

The question is.............are these required and if so, what the fark do i need to do with them LOL:

MTIA
That box on top of the fusebox looks like the the glow controller used on some later vans and other VAG stuff (Caddy/Inca etc.) with IDI engine I think. And no, this is not required as the ECU controls glow period via the new 103 relay.
 

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Sorry if this is in the wrong place I am new to forums .Absolutely awesome work penbryn I am just getting my head round the wiring on my conversion while I am waiting for the gearbox to be overhauled and my VR6 clutch may as well do it right first time.
I just have a couple of questions if you dont mind one of them you have probably answered above but I could not see the pics.I think the black box refered to is what looks like a relay with the number 137 on it so that should be removed ?
I also have another relay marked 53 mounted on top of the fuse box with two red wires and black with yellow wires going to a fuse and then black with yellow going into the loom via a yellow connecter can these be removed or is the yellow black for the glow plug light.Sorry if I seem thick but I have read these posts so many times my head is spinning.
 

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Thanks for the brilliant guide before I start. I've just bought a TDI engine, harness, ECU and pedal box (from a passat) . I've followed the guide and I'm suspicious about a black and white wire that feed into the multiplug. It seems to have been split and has two heavy black wire attached to it that I think led back to the -ve. If you look at the photo you can see that the wire has been split and joined to the heavy black wire via two blue crimp connectors. My question is, what should the black and white wire coming from the multiplug be connected to? Thanks in advance.

 

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Re: 1.9TDI Wiring -Part 2 Engine

The ppl that take the time to do these threads I
Can't thank enough! I'm new to the VW/T4 thing but my conversion is nearly done
thanks to these guys!!!

Tdi power yes please!!
 

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Can any 1 help please???? Ive got a 1999 t4 1.9tdi 800 special, with oil light & rev counter fault, lookin deeper iv noticed the wire is completly missin from the oil pressure sensor (where should it run to??) also theres only 1 wire to my alternator should there be 2??? Please help??? Thanks
 

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right finally getting my head around this loom thanks to penbryns brilliant write up cant thank you enough mate. i have 2 wires left over both black 3 pin connectors.one has black white and yellow wires and the other black/yellow blue/white brown/white any ideas?
also i cant seem to locate the crank position sensor is that one of them.
the loom i have came out of a seat ibiza tdi 110 if that helps.
many thanks
 

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Awesome write up and very informative
I've done a few now so just to add if your using the original dash you will need to modify the wiring for the engine speed sensing
Otherwise your oil light will continuously flash
On my own van the donor car was a 97 seat toledo and the loom was about 1and a half meters longer than a golf item but routed nicely around the back of the battry tray
 

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Re: 1.9TDI Wiring -Part 2 Engine

Just a quick addition to make to this thread. With regards to the water circulation run on pump; the wiring for it is part of the radiator fan curcuit and it connects the same as it came out. When i was doing mine i was unsure of weather it would work but nothing is disconnected so technicly it should T:
Hi just wondering if anyone can help me, I've just done the conversion ABL to 1Z, I have used the 1z flange on the front of the block with the 4 pin temperature sensor on it instead of the one from the ABL with the 4pin and the 2 pin sensors, I am trying to get the water circulation pump running as it should but not sure where the single grey connector in the fuse box from the pump originally connected to?, was thinking of wiring it to pin 7 on G1 which is a switched earth, not ideal as it will be running all the time that the ignition is turned on but at least it will be running, thanks in advance for any help cheers phil
 

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Hi, I came upon this site and thread whilst looking for a solution to a problem with the family Golf 1.9tdi. As it's an electrical problem I thought the poster of the thread my be able to offer some suggestions, please.

History first; The car is a 2001 Golf 1.9tdi SE Automatic 66kw. Engine code ALH Gearbox code FDB. The car was bought new as a Swedish import.

Now to the problem;
The car was left unused for 3 months with a battery known to be on its last legs and due to be replaced when the car was put back into use (now). Needless to say the battery was dead flat and wouldn't show a glimmer of life even when jumped from another car.
I took the battery off and recharged it overnight. Upon refitting the battery (now showing some signs of life) there was instant sparking as though the battery had been connected the wrong way round or charged the wrong way round (it had not).

I obtained and fitted a new battery and found several fuses had blown, including the big one on top of the battery protecting the alternator (so a fairly hefty discharge then!).

Checked ALL the fuses and replaced all blown ones, both on top of the battery and on the side of the dashboard and the one protecting the radio. Everything now worked correctly and as it used to except that the gearbox now wont select 1st or top when in 'D'. 1st can be selected manually, but it wont go into top. As everything worked fine before it was laid up and the battery problem, I assume there is another blown fuse somewhere I've missed. I've had it connected to my local garages fault analyser which shows up as a fault on 'Solenoid Valve N93'. As I've mentioned earlier, there was no mechanical fault last time the car was driven before being laid up, so I can't believe that there is one now. I feel it has to be a fuse or something similar.

It appears that, even if it was a burnt out solenoid valve, they are not available individually and can only be replaced as part of a £600 valve block (unless anyone knows better?).

Any advice gratefully received.

Incidentially, I think some plates may have buckled inside the old battery and caused some sort of an internal short. Quite how that could have caused my problems is a mystery (that is less important now than solving the current mystery!).

Thanks in advance for any help given.
 

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Re: 1.9TDI Wiring -Part 2 Engine

Hi all Sorry not been on in a while but finally decided to take the plunge and do my conversion. Brilliant write ups from aggie and Penbryn. Done everything only one issue. I can find anything regarding the VAN connections anyone shed any light on this. Got the 4 wires red/white brown obviously common earth then the grey/white and yellow (grey 2 pin connector) . The red and white is spliced into several other red and whites. Anyone got idiots guide lol. Probably missed it in the thread.
 

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Hi there

Thanks V.much for all your hard work with the conversion posts I have a garage in cornwall where we have done a number of conversions including a 9A into a mk1 Caddy and various mk1 golf cabbie conversions. This is the first diesel conversion I have done and was following your wiring guide with interest. If I may trouble you with a couple of questions I have a ballast resistor on the mk3 golf donor 97p AHU and the corresponding plugs at fuse box end Black plug with Yellow wire and Yellow plug with Yellow wire. There is also a Ballast resistor on the van. Does this need removing form the TDI loom or leaving in place.

many thanks James
 

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Hi there

Thanks V.much for all your hard work with the conversion posts I have a garage in cornwall where we have done a number of conversions including a 9A into a mk1 Caddy and various mk1 golf cabbie conversions. This is the first diesel conversion I have done and was following your wiring guide with interest. If I may trouble you with a couple of questions I have a ballast resistor on the mk3 golf donor 97p AHU and the corresponding plugs at fuse box end Black plug with Yellow wire and Yellow plug with Yellow wire. There is also a Ballast resistor on the van. Does this need removing form the TDI loom or leaving in place.

many thanks James
Think of the lighting loom for your Ballast resistor I:

Rich.
 
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