C36 Check Engine Light
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Joined: Aug 2009
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From: South Carolina, US
1992 300E, 1995 C36 AMG, 1969 VW Bug
C36 Check Engine Light
CEL came on last night, car is driving and running perfectly fine.
Took it to an Autozone to have the code read, guy said because it's a '95 he can't read it since the reader is OBDII and obviously 95's are OBDI. I asked him to read it anyways for me, which he did.
Code reader said random misfire on cylinder 1 and also P1700 (delay upshift valve failure).
The car is definitely not misfiring. I had a misfire on cyl. 3 last year due to burned out plug wires, the car ran like **** and felt like a 50 year old diesel truck. Car runs and pulls fine now.
Also, the delay upshift valve seems to be working. On a cold start the car holds the 2-3 shift until it's warmed up, like it always has.
I haven't been driving the car much, I started it last weekend for the first time in a month to do an oil change. It ran a little rough since it hadn't been started in so long but smoothed itself out after about 5 minutes.
Is it possible that during those few minutes of rough running there were some misfires on cyl. 1 and the OBD system logged them and is now giving me the CEL because of them? What about that P1700? Is it possible the OBDII reader is just giving bogus readings that do not apply to my OBDI car?
Thanks
-Paul
Took it to an Autozone to have the code read, guy said because it's a '95 he can't read it since the reader is OBDII and obviously 95's are OBDI. I asked him to read it anyways for me, which he did.
Code reader said random misfire on cylinder 1 and also P1700 (delay upshift valve failure).
The car is definitely not misfiring. I had a misfire on cyl. 3 last year due to burned out plug wires, the car ran like **** and felt like a 50 year old diesel truck. Car runs and pulls fine now.
Also, the delay upshift valve seems to be working. On a cold start the car holds the 2-3 shift until it's warmed up, like it always has.
I haven't been driving the car much, I started it last weekend for the first time in a month to do an oil change. It ran a little rough since it hadn't been started in so long but smoothed itself out after about 5 minutes.
Is it possible that during those few minutes of rough running there were some misfires on cyl. 1 and the OBD system logged them and is now giving me the CEL because of them? What about that P1700? Is it possible the OBDII reader is just giving bogus readings that do not apply to my OBDI car?
Thanks
-Paul
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From: Chapel Hill, NC/Montreal, QC
1995 C36 AMG, 1998 C43 AMG
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From: Henrico, Virginia
2014 ML350 4Matic
P1700 is a failure of the upshift delay feature for the 2-3 shift when cold. That shift is delayed when cold to heat the catalyst quicker, which puts the ECU into closed loop, hence the code set if it fails.
I am pretty sure it is the same as on the regular C280 for that year. There is a solenoid in the electronics area of the double firewall. The solenoid applies vacuum to a vacuum box on the transmission pressure modulator control cable that runs from the throttle linkage to the valve body. Check the vacuum lines. However, in my experience, the vacuum box on the cable is usually the problem. You can test it by applying vacuum at the solenoid and checking the cable at the throttle linkage end - pull it off the ball end and feel for a difference with and without vacuum. It is a PITA to change out, but I have done it a couple times with the transmission in place. You have to drop the pan to make connecting the end of the cable to the linkage inside the transmission reasonably easy. Also, the locking cam that holds the cable/vacuum box in place on the right side of the transmission is almost impossible to see. You have to work by feel and with a mirror.
I don't think I would worry about the misfire at this point.
I am pretty sure it is the same as on the regular C280 for that year. There is a solenoid in the electronics area of the double firewall. The solenoid applies vacuum to a vacuum box on the transmission pressure modulator control cable that runs from the throttle linkage to the valve body. Check the vacuum lines. However, in my experience, the vacuum box on the cable is usually the problem. You can test it by applying vacuum at the solenoid and checking the cable at the throttle linkage end - pull it off the ball end and feel for a difference with and without vacuum. It is a PITA to change out, but I have done it a couple times with the transmission in place. You have to drop the pan to make connecting the end of the cable to the linkage inside the transmission reasonably easy. Also, the locking cam that holds the cable/vacuum box in place on the right side of the transmission is almost impossible to see. You have to work by feel and with a mirror.
I don't think I would worry about the misfire at this point.
Thread Starter
Member
Joined: Aug 2009
Posts: 134
Likes: 0
From: South Carolina, US
1992 300E, 1995 C36 AMG, 1969 VW Bug
Upshift delay is working properly.
Cleared the CEL a few days ago and it hasn't come back on, but I don't drive the car that much.
Not really sure what to do at this point other than just drive it a little more and see if the light comes back on.
Cleared the CEL a few days ago and it hasn't come back on, but I don't drive the car that much.
Not really sure what to do at this point other than just drive it a little more and see if the light comes back on.
