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Drive Cycle???

08-22-2005, 06:05 PM
Great forum! I'm afraid that I am one of those people that has to ask more than he can contribute. Sorry. I'll try not to be too much of a nuisance.

I am trying to get a '96 Jetta Trek, 2.0, 5 speed, through CT emissions. First time it failed with codes P0102 (MAF Sensor) and P0131 (Forward O2 Sensor). I removed and replaced them both, took the car to someone with an ODBII computer, he cleared the codes, and the Check Engine Light (CEL) went out. After driving the car about 50 miles the CEL came back on. I returned the car to the shop with the ODBII and he scanned a code P0411 (Secondary Air Injection System). He and I looked it over and decided that the most likely problem was with one of the worn vacuum hoses. The hose was removed and replaced, the codes were cleared with the ODBII, and the CEL went out. I went back to emissions this morning for the retest. The emissions tech called me in to show me that his computer could not read anything. He said that after the codes are cleared in the ECM, a 'drive cycle' must be entered to reboot the ECM. I looked at him like I was stupid, so he explained that each manufacturer has a specific set of 'rules' that have to be followed to make the ECM readable again. He gave an example of something like, "You have to drive it maybe between 0-30 for five minutes, then maybe 31-45 for ten minutes, then maybe 46-55 for five minutes." Now I looked at him like he was stupid. He said that he didn't know the 'drive cycle' for Volkswagens and that went I had the ECM working to return for retesting at no cost.

There aren't any VW dealerships within 20 miles, so I went home to call them for verification. Two other emissions testing stations agree with what the first one told me. I got three different answers from four dealers. Two said they never heard anything so stupid in their lives (or words to that effect), one said it simply had to be driven 30 miles at any speed, and one said that if I simply drive like I normally do that over the distance of 500 miles I will surely 'stumble onto the 'drive cycle perameters'.

I feel like I have either crossed over into the twilight zone, or I am being filmed on Candid Camera. Does someone in here REALLY know what's been happening to me and how I can end this madness? I know this is long, but I wanted to be thorough. Gary

08-23-2005, 08:00 PM
Each of the major systems (for most OBD-II cars there are usually 8) has a time period in which a certain set of events must take place in order for the computer to determine that system is working properly. The time, mileage and driving conditions vary, but usually this occurs within 20-100 miles of normal driving. An inability for the emission scanner to access your car's computer is something entirely different. IF the CEL comes on at startup & goes off the system should be accesable, the problemm ay lie in the connection or connector. Try a major auto parts seller, most of them have generic scanners that can access your car.

08-24-2005, 06:46 PM
I think I've got this all figured out now BOSCHMANN, not fixed, but figured out. When I returned to emissions for testing he could not get readings from the major systems because I had just had the ECM codes 'cleared' 3 miles ago. I'm now sure that the ECM has to receive a specific number of signals from each system before it can respond to it, and 3 miles was definately not enough. When I put 231 miles on the car after it had been cleared, the check engine light came back on, so I guess that that's the magic number for a code 0411.

I have talked to a couple of guys that are familiar with VW's and both of them think Ishoulg replace the relay. I don't like the idea of replacing parts without knowing something is wrong with them. The air pump is functioning and I cant find any vacuum leaks. Care to take a guess yourself?

08-26-2005, 04:37 PM
First run a 12V power and a ground wire directly to the SAI pump to be sure it works properly. Next, follow the pressure hose from the pump to the valve on the manifold & check the vacuum line from the valve back to the electric solenoid & from the solenoid to the intake. If all are okay you can check the electric solenoid by running power & ground to it. Air flow should start/stop with current application.

08-27-2005, 01:09 PM
All of that checks out; however, I see that the air pump is not being supplied any power with the engine running. I'm assuming that it should be running even at idle. I cannot trace the wires through all the mass wrapped wires. Is there a fuse or relay that powers the air pump?

08-28-2005, 11:42 AM
The pump will only run for a few minutes at a cold engine start. It is fused, I'll have to look the location up & get back w/you.

08-28-2005, 03:21 PM
I found it; well, I found a blown fuze. There was a 40 AMP in-line fuze coming off the positive post of the battery. The air pump now comes on at cold start up, but stops after about a minute. I tried clearing the codes by leaving the battery disconnected overnight, but after 13 hours its still comes back on. I'm going to take it tomorrow morning to have the codes cleared then drive it another million miles to see if the CEL comes back on. Hopefully I've found the problem. Thanks for your help.

08-29-2005, 08:10 AM
When I went to clear the codes, a new code shows up now...P1420 - Secondary Air Injection Module Short to B+. Is this something new that is wrong or is this something that I caused when jumping the relay/air pump while the engine was running? Will it cause the CEL to come on again after I complete the drive cycle? If so, how do I fix it?

08-30-2005, 08:05 PM
Did this code come back after clearing & driving?

08-30-2005, 10:03 PM
The CEL hasn't come back on. The car has about 200 miles since I cleared the code. Whether that is enough miles to be considered the 'drive cycle', I don't have a clue. If I don't get a CEL by Friday noon, I'm going to schedule the retest at emissions. We'll see.

08-31-2005, 05:31 PM
Well, the CEL came back on. 297 miles after clearing it. I haven't scanned it yet so I don't know what's wrong. I just ordered an ACTRON CP9135 OBDII scanner. ($250 for a VAG COM just isn't worth it to me on a car with 130K+. Besides, I have other ISO systems in my driveway.) I just can't continue going to other people with my hat in my hand to get it scanned. I've done that five times now. It's 60+ miles round trip to get a free scan at someplace like Autozone, so I'm just kind of screwed. I'll let you know how it goes.

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