HowardP
Active Member
- Joined
- Jul 13, 2018
- Messages
- 84
- Location
- Milton Keynes, UK
- Car
- 1989 C126 420 SEC (SOLD); 1985 W123 200 (SOLD); 1993 W124 320 CE CABRIOLET; 2012 W246 B180
I have discovered that my automatic 5 speed 'box changes straight from 3rd to 5th. I have tested this by moving the selector from D to 4 at just over 60 mph, but nothing happens, it just stays in 5th. The RPM at 60 are about 2,300, which seems to be correct for 5th gear. Other than the missing 4th gear the 'box behaves normally, both up and down the gears.
I have repaired the switch behind the selector lever, but that made no difference.
It has been suggested that I should check and clear the Diagnostic Trouble Codes (DTC) through socket 13 of the 16 socket diagnostic port.
I have borrowed a blink code reader, but when I insert the test plug into socket 13 the LED illuminates immediately and stays on. When I press the momentary on button, the LED just glows a little brighter.
Interestingly, and perhaps worryingly, the LED stays on when I disconnect the code reader's earth plug, although the LED remains unchanged when I press the button.
I have used the code reader on socket 6, and it works perfectly, so it would appear not to be the code reader at fault.
I am wondering if there is a deeper electrical issue, such as short circuit, which is affecting socket 13, and perhaps the gearbox.
Any advice (in layman's terms) would be appreciated.
I have repaired the switch behind the selector lever, but that made no difference.
It has been suggested that I should check and clear the Diagnostic Trouble Codes (DTC) through socket 13 of the 16 socket diagnostic port.
I have borrowed a blink code reader, but when I insert the test plug into socket 13 the LED illuminates immediately and stays on. When I press the momentary on button, the LED just glows a little brighter.
Interestingly, and perhaps worryingly, the LED stays on when I disconnect the code reader's earth plug, although the LED remains unchanged when I press the button.
I have used the code reader on socket 6, and it works perfectly, so it would appear not to be the code reader at fault.
I am wondering if there is a deeper electrical issue, such as short circuit, which is affecting socket 13, and perhaps the gearbox.
Any advice (in layman's terms) would be appreciated.
