Checksum errors

Igor · Post by **Igor** » Sat Oct 13, 2007 10:10 pm

G'day,

I've been messing with the Tuner Pro RT for datalogging from my (don't laugh) Lada Niva - Russian 4x4, 1.7 litre. These had single point injection systems fitted that were supplied by GM during the mid 90's before they switched to Bosch multi point systems. The sticker on the ECM housing identifies it as an ECM type is 16186499 - I think, it communicates via a OBD1 link and I'm using this cable
http://www.aldlcable.com/sc/details.asp?item=aldlobd1

The ECM is 8192 baud unit.

I've modified the original ads file supplied with Tuner Pro to something that was working very well for about 2 weeks, but now has stopped working.

I get correct data transfer when the engine is off but ignition is on, but the moment I start the engine, packet errors begin, data comes sparodically and usually only when the engine is decelerating. The code I'm using to get the ALDL datastream to flow is $F4, $57, $01, $20, $94. I've also slowed the sampling rate to 4Hz which seemed to help in the initial set-up. As I said before, this was working perfectly 2 weeks ago - so I really don't know what has changed.

When I check the output using Carbytes, again everything is fine when the engine is off but once started, replies from the ECU slow down and Carbytes says I'm now getting checksum errors. Has anyone come across this before and more importantly is there something I'm doing wrong here?

The notebook I'm using is a 450MHz K6 II.

Igor

Post by **Mangus** » Sun Oct 14, 2007 2:41 pm

Very interesting, Igor. This sounds like there could be a wiring issue. Have you ensured that everything is grounded and that the connection between the ECM and ALDL connector is solid? Perhaps there's a short somewhere.

I notice that the ALDL cable you linked to uses 12v power - that might be the problem as well. Perhaps you could try one that doesn't require power (such as a USB cable from moates.net, or a serial cable from AKM cables). I've heard noisy 12v power being an issue with these types of cables.

If you have the resources, would be to try a different cable and maybe even a different laptop, although the laptop is probably not the culprit.

I'd start by checking all of the harness wiring and make sure everything looks good.

Six_Shooter · Post by **Six_Shooter** » Sun Oct 14, 2007 3:13 pm

To eliminate the possibility of a noisy power source, you can use a 9V battery connected in place of that plug, or to the plug as it were.
That is how my home made max232 based cable is and works fine.

Igor · Post by **Igor** » Sun Oct 14, 2007 7:26 pm

Thanks for those quick replies.

I have a 240 V AC (I'm in Australia) to 12v DC transformer I can try in the garage to see if this is the right direction.

It could well be noisy power, I believe the original alternator is on the way out and at times the Russian electrics can be frustrating.

I also checked last night and found some Russian websites which confirmed the ECU number I placed in my original post. I'll pass on the .ald file when I get it sorted - there are thousands of these cars kicking around both eastern and western Europe which could benefit from your software.