[SoCal LS-L]

I thought id add my experience to this thread, since Ive seen a lot of Code 56 issues.

If your EGR temp sensor looks anything like the original posters, you can be assured the piping from the EGR valve to the sensor, and from the sensor to the intake tube to the manifold, look identical. After I removed my EGR valve, I sprayed Brakeleen, using the straw stuck into the top hole and fed into the tube running downwards, and the result was a large mass of black goop and grit coming from the base where the EGR valve sits. I mean TONS of crap.

After that was cleared out, I took a hard plastic weed-eater line and carefully pipe-snaked the tube that went the other direction toward the intake manifold... the reason being I didnt want to spray brakeleen into that side and force the grit and crap into my intake and engine. I fed the line in (with a little crook in the end to scrape up stuff), and after it went far enough in (no more resistance), I pulled it out slowly using a twisting motion. It took about 30 repetitions until the line came out without tons of black grit and goo..... the EGR tubing had been plugged up this whole time with this crap.

This has since FINALLY rid me of the EGR code 56.... as the temp sensor could not detect any temperatur change since there was no exhaust gasses flowing by it, since it was completely clogged. I would recommend anyone with a 56 code inspect the temp sensor porting, its almost assured it is clogged with crap after 11-17 years. This should be done, along with inspecting the flow through the vacuum lines to the EGR vacuum control, before blowing money on replacement parts. Hopefully this helps someone else out, because having an eternal MIL is a pain in the ace and ive noticed a lot of EGR related issues here.