I previously posted that I was getting a recurring P1602 alarm on my 1999 Audi A4. The alarm was occurring without disconnection of the battery. At first I though that one of my temperature sensor faults or throttle body faults may have been causing the P1602 to keep showing back over. After replacing those parts I still had the recurrning P1602. At any rate, I have found the source of the fault and wanted to post what I found as I could find no mention of this type of issue on any of the forums I review frequently.

The amazing thing is that what was causing my alarm is the same mechansim one of my co-workers was told was wrong with his BMW. He was told that his CEL light was on becasue a slow radiator fluid leak at his thermostat resulted in the radiator fluid "wicking" up his wiring harness back to his engine control module (ECM). In priniciple this makes sense, but I thought was highly likely. However, after enough trouble shooting on my Audi I chose to inspect the ECM. Amazingly upon disconnecting the wiring harness to my ECM I found radiator fluid had wicked up through the harness and into the connectors. When I pulled the ECM out I could see fluid inside the connector housing on the ECM (not actually inside on the board as I checked that as well). At any rate after cleaning up the exposed fluid I reset the P1602 alarm and it has yet since come back on and has finally allowed me to get my emissions tested. The P1602 resulted in the readiness code resetting every time I turned the ignition off so my emissions always failed.

Again, I have never seen a posting showing anything like this, so I thought I would forward out as it is a bit unusual that I have yet to see mentioned in any forums.