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Old 04-22-2003, 12:12 AM
Posts: n/a
Fault 26 Upshift delay switch over valve-open or shorted

Check Engine light came on after driving 90 miles and the cruise control worked intermittently [Doesn't always engage but when it does it continues to work]. Checked for the fault code.
“Fault 26, Upshift delay switch over valve-open or shorted.” When I was checking for the code with the key in the on position I was getting a high pitched wine accompanied with a sound like relay contacts clicking coming from the driver side near the bottom of the engine. I could not locate the source.
I disconnected the leads to the switch and they seemed find. I tired to trace the vacuum line to the transmission but couldn’t find the termination connection. Do you have to get to this from the inside of the car? I checked my stop lights and noticed that the right side one’s glass was slightly discolored and that the silver contact was melted like an angular knife cut with a bead at the incline high point. Never saw that before so I replaced it. The bulb was a 12498 Philips and the filament was intact.
The Check engine light is off for now and the noise is gone.
I have been having problems with the cruise control all winter and was blaming it on the cold.
What do I need to do to check this out if it reoccurs?

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Old 04-22-2003, 08:10 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
The cruise control is controlled by the EA/ISC/CC computer, have that computer scanned for codes. Sounds like the throttle actuator might be on its death bed.

The code 26, up-shift delay means that the transmission didn't hold in gear long enough durning warm-up. Usually a vacuum leak at the control cable.
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Old 04-23-2003, 04:30 PM
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Join Date: May 2002
Location: Jacksonville, FL
Posts: 1,142
Does anyone have a picture of the location of this control cable as mentioned earlier....

"The code 26, up-shift delay means that the transmission didn't hold in gear long enough durning warm-up. Usually a vacuum leak at the control cable."
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Old 04-24-2003, 12:42 AM
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What are the Transmissions Symptoms for Fault 26

What symptoms does the transmission present when this fault code 26 is in affect? I've always had a little jolt in mine ever since it was new and this usually occurred intermittently when I am accelerating from a stop, it comes and goes. The car could be cold or have been driven a lot of miles it doesn't seem to matter.
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Old 04-24-2003, 07:39 PM
Join Date: Dec 2001
Location: Southern California, U.S.A.
Posts: 8,538
The upshift delay valve delays the upshift from 2nd gear to 3rd gear when your car is cold. In other words, it keeps the car in second gear longer in order to warm up the catalytic converter quickly to reduce emissions.

The usual suspect when you get a code #26 is the upshift delay valve itself, which is located on the side of the transmission. They usually fail because they fail to hold pressure, i.e., they leak.

You can test it to see if it holds pressure by pulling the green vacuum line from a switch that is located on the fire wall, behind your brake master cylinder. It is the only thing there, and you will clearly see a green line and a black line (electrical) going to it.

Pull the green hose, and attach it to a hand vacuum pump, and pump some pressure in it. If it leaks, it will be obvious. If there is no leak, then probably that switch is bad.

There is a lot in the archives on this, too, so try experiementing with the search function.

Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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