Trouble with SAI DTC 16795

Hello everyone, I tried to do a search on the forum for this but did not pull up anything. I have been trying to diagnose a DTC 16795 on my daughter's 1998 Audi A4 V6 (30 valve). I have verified that the smog pump is functional, that the relay is working (tried multiple replacements with no change), and the fuse is working as there is power to both terminals at the relay. When I jump the relay and provide direct power to the smog pump at the relay location it turns on. We already replaced the vacuum lines when the did the engine tune up... and this problem existing before then when we bought the car. What would prevent the smog pump relay from activating and produce this code? I am thinking the solenoid on the top of the motor towards the firewall might be the culprit based on the Ross-Tech FAQ on this... part #026-906-263-H? Anyone have an opinion on the problem?

David

Welcome to the forum David.

You will be asked to post a full AutoScan from the vehicle in between [CODE ] your code [/CODE ] code tags without the spaces.

http://wiki.ross-tech.com/wiki/index.php/16795/P0411/001041

Can your VCDS this key on engine off (KOEO) log in to engine 01 and perform out put tests.
One should be to close the relay and run the pump. This will tell you the ECM and wiring are good if the pump runs in out put test.
Another out put test should be the Noid for the SAI it should click.

With engine running check Vac. supply to the noid and vac. lines from the noid to the kombi valves V6 should have two.

Good Luck

How about the fuse...........?

Can it carry current not just voltage?

Have you attempted 0x01-03 to operate the relay via ecu to test the driver?

Thanks everyone, I was only able to do a quick scan yesterday since my daughter had to leave... I will do some of the tests mentioned above and post a full scan once I can get access to the car again.

David

You can call for the SAI test directly....... car running........ at idle in VCDS 0x01-04-077 or 160 depending on control unit.......

Just a final update on this... wow, what a fun ride troubleshooting this was! Thanks to the feedback from you guys I did the output tests and everything seemed to be okay. However, the smog pump was still not turning on. I rechecked the relay location by jumping the terminals with the relay removed and the smog pump turned on... whats interesting is that the relay was clicking as it should. I ended up going to a local pick-n-pull junkyard and gathered a handful of the relays from other Audi's. Testing with them resulted in the same thing, clicking but no smog pump turning on.... that is until I tried the fourth relay, suddenly everything worked! So when trying this troubleshooting be aware that even though the relay can "click" it may still be malfunctioning!

David

WunderWagen said:

Just a final update on this... wow, what a fun ride troubleshooting this was! Thanks to the feedback from you guys I did the output tests and everything seemed to be okay. However, the smog pump was still not turning on. I rechecked the relay location by jumping the terminals with the relay removed and the smog pump turned on... whats interesting is that the relay was clicking as it should. I ended up going to a local pick-n-pull junkyard and gathered a handful of the relays from other Audi's. Testing with them resulted in the same thing, clicking but no smog pump turning on.... that is until I tried the fourth relay, suddenly everything worked! So when trying this troubleshooting be aware that even though the relay can "click" it may still be malfunctioning!


David

Click to expand...

Then the contact surface is worn, you could inspect that with opening the relay or applying voltage to coil terminals and checking resistance between the switching terminals.

Probably true, but I would rather just replace the relay.

Ahhhhhhhhhhh why just inspect........wanna play full out junk yards wars?

Take relay apart.
File the points to make the contact better with fine file and then 2000 grit sand paper and tug the tension spring a tad to make a better contact grip.

Then reflow the solder joints.

See what I was saying about carrying current verse seeing just voltage?

Remember use the force and you will find your way............. use your eyes and they will trick you..........

Technique less fancy than that got the fuel pump relay in Eric's bike working well enough to get from the Redneck Riviera back to PA!

-Uwe-