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Discussion summary
YOUR RESEARCHPSM Switch Problem
Leading reported evidence
Check emissions at 2 rpm ranges
Suggestion or failed attempt
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Suggestion
I had my car smogged earlier this year and all they did was to check for emissions at 2 rpm ranges.
Leading evidence: 'Check emissions at 2 rpm ranges' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check emissions at 2 rpm ranges' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
The only way to disable it would be to disconnect the drive shaft to the front.
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Suggestion · Original poster
In CA they have to run the car on the dyno to pass emissions.
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Suggestion
In BC smog tests are run on dynos for cars without OBD.
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Suggestion
I had to run out and turn the car off myself (over their sceaming at me that I could not be in the testing area) before the burned it up.
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Hi,
I have a 2001 Cab Tip. Have to go get a smog, but need to turn off the PSM (so they can run it on the dyno). However, the PSM switch will not respond when I press it.
The "PSM Off" idiot light still lights up (and then turns off shortly afterward) when I start the car. I pulled the fuse on the PSM control unit and verified the PSM light didn't turn on when I started the car.
I did a search on this board, but couldn't find anyone with a similar problem. I assume it could be as simple as the switch on the dashboard. Anyone seen a problem like this?
Thanks,
Chris
wy are they running it on a dyno... they can just plug in and KNOW how it is running - that doesnt fix your problem..... but its dumb to dyno your car for a smog test
Be very careful, is yours a C2 or a C4. If it is a C4 it must be a 4 wheel dyno, and most smog test stations won't have this. In illinois all they do is plug in their equipment to the OBD port and get all the info from the on-board computer.
Years ago I had a 928 with first gear to the left and down (where second gear is on a 996) and reverse to the left and up (where first is on a 996). At the smog station they put it on a dyno, and required that I leave the area and sit in a waiting room. Then put the car in reverse and started to rev it up to ge to speed. I had to run out and turn the car off myself (over their sceaming at me that I could not be in the testing area) before the burned it up. The testers are basically low-paid low qualified employees. Again be careful!
I agree that it's dumb, but California smog law is that all smog data be taken at two particular RPMs while the car is under load. Not sure where Chris is, but prob the same deal.
Dharn55, how'd you know that they were gonna smoke your car? Could you hear something wrong, or were the front tires slipping on the pavement??
Can't the FWD be disabled on the C4?? I thought I heard that it could.
There must be special AWD dynos for smogging CA (and other) cars, but never thought about it until just now (haven't had mine long enough, and had the previous owner get it smogged before I bought it since that's CA law too).
Hey Guys,
Mine is a C2. I am also in San Diego. In CA they have to run the car on the dyno to pass emissions. It sucks that this problem will keep me from doing the smog check.
I ordered the PSM switch from Pelican, hopefully that fixes the problem.
Thanks
Chris
On a C4 there is a minimum of 5% of the power going to the front wheels. The only way to disable it would be to disconnect the drive shaft to the front. So a 4 wheel dyno, or a way to raise the front to let the wheels rotate is necessary.
As for smoking the car, this was on a 1982 928 with rear wheel drive. they had the rear wheels on the rollers, but had the car in reverse and started to accelerate. If they had reved it to high (to get to the speed they wanted) or tried to up shift the engine/trans could have been ruined.
It turns out that there is a fuse other than B1 and B9 (both of which have PSM in their title in the fuse guide) that powers the PSM Off switch. Apparently that fuse was missing in my car. Not sure which fuse it is, but its a 15A fuse.
california, the c4/c4s/turbo are exempt from the dyno. I had my car smogged earlier this year and all they did was to check for emissions at 2 rpm ranges. that's it.
