How-to: Make a Diagnostic cable for your VN/VP Commodore

[richie83]

After seeing a few people have trouble making these cables, or getting them to work, I've written up a small tutorial, with a revised edition of the schematic (Thanks Chuff for (parts of) your drawings).

For this Tutorial you'll need:

A soldering iron
Some solder
Pliers (long nose are especially useful)
3 x 10kOhm 1/4 watt resistors
1 x 9 pin RS232 plug plus casing
1 x ALDL wiring connector, Supercheap part AERPRO Model No. APP0141; Car stereo wiring harness to suit Toyota Camry 87-89, Celica 87-96, Corolla 87-96, Land Cruiser 87-96
1 x length of cable, can be Cat5 cable, security cable. Must contain at least 3 wires. (1 to 2m is good, maximum 9m).
Some electrical tape, or if possible, some small heat shrink.

NB. Tinning is the practice of soldering wires to prepare them to be soldered to another wire.

Firstly, grab the wiring harness you bought from Supercheap and go match it with your cars ALDL connector. This is the connector you want. Cut of the excess connectors, and try to leave as much cable on the plug as possible. Pull the cables out using long nose pliers on all pins. Re-insert singular wired pins (some of the pins have 2 cables on them) back into pinholes 1 and 3. Cut the cable off 2 of the pins, and insert two of these pins into pinholes 2 and 4 (these help in guiding the connectors together). Strip the insulation off of another pin, then cut it back so some copper remains (about 1 cm). Tin this with solder. Tin one of the resistors with solder, and join the resistor to the pin you stripped. grab another pin, and from the pin end, strip the insulation to reveal some copper. Dont strip it completely! Tin this small segment of copper, attach the other end of the resistor to this segment. Push these pins into pinholes 5 and 6. Onto the Serial end.

This bit takes some fiddling. Grab the serial connector. If you look closely, you can see the pins are numbered on the back and front (If not, the view in the diagram is from front of the connector). Snip some of the leg of a resistor, and put it into pin 2. Place the transistors collector leg into pin 2 also. Now solder these into the pin. Put the emitter leg of the transistor into pin 5 on the connector. Grab the cable (the cat5, etc.) and strip the sheath back (outer insulation) about 5cm. Cut all but 3 wires off. At this point, note which wires you are going to use as Data, Ground and Voltage. Write them down! Data attaches to the resistor coming off the base of the transistor, Ground to the emitter and Voltage to the resistor in pin 2. Strip one of the wires back about 1 cm. Place it into pin 5 on the connector, and now sodler the wires in pin 5. Now, bend the base of the transistor back on itself (as if it were pointing at the cable). Shorten the resistor, about 1cm of leg at each end is good. Tin both ends of the resistor, and the base leg of the transistor. Solder the resistor to the base of the transistor. Tin the other end of the resistor in pin 2. Attach your Voltage wire to this (remember, you wrote it down!). Solder your DATA wire to the resistor coming off the base of the transistor. Put some tape around the cable, and attach the small metal bit that stops the cable from pulling out of the RS232 connector. Put it all in the case, and screw it up.

Now, get the other end of your cable. Strip the sheath back about 5cm. Cut out all the wires except the ones your using for DATA, Voltage and Ground. Strip back the 3 wires from the ALDL connector, about 1cm. At this point, if your using heatshrink, its a good idea to cut 3 small pieces off, and put them on the cables. Tin the bare copper on each of the wires. Now strip the insulation off your 3 wires on your cable, and tin them aswell. Now solder your DATA wire to the wire on pin 3 of the ALDL connector. Then solder your Voltage wire to the wire on pin 1, and lastly your ground wire to the wire on pin 6. Put the heatshrink over the soldered joints, and either gently touch it with the soldering iron, or use a hairdryer/hot air gun to srhink it. If your using tape, wrap some around the joints. We definetely don't want them touching. Wrap some tape from the connector, all the way to where the sheath starts on the cable.

Voila, your done! Now all you need to do is connect it up to your laptop, and start logging with WinALDL; http://winaldl.joby.se/ .

If anyone has any queries, questions edits or comments, feel free to post, or message me. Enjoy

 

[ViperVp]

Good work there very well writen... i should have made one for mine.. but i got it from ebay awewell it works so thats the main thing.

 

[markovr]

is there one for vr/s commodores?

 

[richie83]

is there one for vr/s commodores?

Yep there is, check out the other ALDL thread. I made this modified one, since some of the info for the VR/VS one was different to the VN/VP one (different connector).

 

[MaNiac_VP]

Great work there, Ill make it sticky!

happy new year, cheers Paul

 

[richie83]

If anyone wants a cable made up for their VN/VP for just the cost of parts + shipping, message me. Its currently at $35 per cable (inc. shipping to any state), but could become lower if I manage to contact AERPRO about getting either the harness' or connectors seperately. If I can just purchase the connectors seperately, the price could drop to around $10 for the cable.

Im also in contact with the author of WinALDL about whether he's interested in developing it further, or if I/someone else could take over (limited programming skills here).

Lastly, Im hoping to find some individuals with up-to-scratch cars who have cables, or who live in Perth so I can gather some data on different types of cars, and go down the track of diagnosing problems via ALDL rather than us spending hundreds at Holden dealers. I know the older models are getting long in the tooth, but it seems a lot of owners are hanging on to the cars. Even if we can start the same sort of thing with VR/VS all the way through to the VY (No idea about their ALDL characteristics) it might prove a good hobby for most.

If anyones got any ideas or suggestions, feel free to message me.

 

[pete_pumpkin]

Hi guys, is anyone having trouble getting everything working correctly?

I built a cable up and in winaldl I get 3 or 4 streams coming up when the car is in acc, but as soon as I switch the engine on the stream of data stops.

I built the cable using a bc559b and then tried a bc548. I later realised that there is a recommended list of transitors that I was meant to use. Anyhow I bought some 2n2222 today and chucked one in. I still get the same problem. This time at first I had a few more bits of data coming through, all the way to 'tps' but again as soon as I switched the engine on the data just stopped.

Also particulary when I used the other transistors and started the engine, I started to get a very rough idle.

Originally I was taking the 12v supply from the the car, but since have connected it directly from the serial port.

Anyone have any idea what's going on?

Pete

I'm driving a 93 VP BT1

As for laptop I was using a 233 with win2000, and have also tried a 133 with w98

 

[abzy]

Ok ok, Stupid question from me.

What does this cable actually do?

 

[pete_pumpkin]

abzy ...google is your friend


Anyhow I managed to get it working by modifying the circuit on techedge:http://www.techedge.com.au/vehicle/aldl160/aldl_hw.htm

I had to remove R4 to get it to work though.
Also take note that the 'colour codes' for the resistors are messed up so don't go by them if you choose to build this circuit. ie black brown orange should read brown black orange and so on.

I'm still a little dissapointed as the rate at which the data is read is really slow, approx a sample per second at 2400 baud. This is pretty crap if you don't mind me saying. You can set the programme (winaldl) to 4800 but you end up loosing 3/4 of the data and the dash and sensor data don't show anything.

I mainly wanted to know 02 info, but my figures are jumping all over the place from extremes such as 0.05V to 0.8 Also with the cable connected the car idles really badly and I think it's making the car run rich.
Without the cable connected the car idles fine.

So yeah I don't know what the deal is, I just realise there is lot of stuffing around and I've got lots to learn interpretting all the data

Fellas let us know what your experiences are :b:

 

[richie83]

Firstly, my cable doesn't affect my cars idle. I think your problem may be the wiring of your circuit. If your running in open loop mode (running the car with the diagnostic pins short circuited) you will experience reduced idle, as it disregards any fuel trim data. This could happen because you have a short where the 10k resistor is supposed to be. If your having serious troubles, try building the whole thing on some project board where you won't have problems shorting wires squeezing it into the DB9 connector.

Secondly, your O2 values will jump. They should be jumping from high to low constantly. The computer only detects an O2 fault if a low or high reading (or open circuit) is detected for a specified amount of time. This time increases when cruising. So don't stress, your O2 values are reading correctly. If you graph these over a long enough time, you should be able to get an average, and create a straight line, if the O2 sensor is dodgey, you'll have dips in the 'average' line.

Thirdly, you can't read data any faster. 160 baud is the rate at which data is sampled. This is a restriction of the cars computer, not of the cable or computer/laptop. Theres no way you can sample the data any faster, unless you own a VR/VS which have a different ALDL baud rate, and thats a whole new cable setup. If you take data over an extended period of time (30 minutes gives good results) then you can actually find some good information. The design I've used works perfectly on VN/VPs. Now Im just working on a 'standard' set of data, so people can compare.