“Engine Breaking” (B Gear) Stopped Working

[Mikeg02222]

When I shift down into second and then over into the B position the car does nothing. It used to shift into first gear and hold it until shifting back over into second. Now it just stays in first and second in both positions.

I pulled the blink codes and came back with these. I tried to include the “reason” from the DTC sheet. I’m assuming it has something to do with one of the pin 8 codes but would like to hear some input from you guys. Fuse 7 was blowing when I’d shift into B but it no longer does
side note: should I be concerned about any of the other codes? Are any of them easy fixes?
Thanks in advance!

 

[gsxr]

Pin #8, code #15 is indicating a fault with the kickdown solenoid circuit. You'll need to trace that out and determine which component is the problem. See diagram below, ignore K29/1 if your car is an E500E. Might be a wire shorted to ground or something.

Clear all the other codes and see which ones return. If your car is a 400E/E420 and has ASR then you'll want to fix the starter lockout / NSS (pin 7 code 6) as that can cause limp mode.

 

[Mikeg02222]

Pin #8, code #15 is indicating a fault with the kickdown solenoid circuit. You'll need to trace that out and determine which component is the problem. See diagram below, ignore K29/1 if your car is an E500E. Might be a wire shorted to ground or something.

Clear all the other codes and see which ones return. If your car is a 400E/E420 and has ASR then you'll want to fix the starter lockout / NSS (pin 7 code 6) as that can cause limp mode.

View attachment 136102

The car is a 95 420. When I was pulling the codes I was also clearing them and the pin 19 codes would clear at all. The rest cleared but I haven’t checked to see which ones have come back. Do you know where I can find a guide to all of the switch codes?

 

[gsxr]

Pin #19 may require re-starting the engine to fully clear the codes. Code translation guide is at this link. Info on the NSS is at this link.

Does your E420 have ASR?

 

[Mikeg02222]

Pin #19 may require re-starting the engine to fully clear the codes. Code translation guide is at this link. Info on the NSS is at this link.

Does your E420 have ASR?

Yes it does. Thank you for those links! I have two spare 722 transmissions from m104s. Are those neutral safety switches the same? Is it worth messing with a used one or should I buy new?

 

[gsxr]

Unfortunately, nope, the M104 NSS is different... does not have the 4 additional small pins which provide a gear position indicator to the E-GAS module for the ASR system. Don't mess with used, buy new, ~$100 or so. If it's original, it's due for replacement. Make sure it's adjusted properly during installation, and also verify that both shift linkage bushings are in good shape. The linkage should have zero play.

 

[Mikeg02222]

I’ve already got a transmission filter waiting to be installed. I’ll add that to the cart and get one on the way. What are your predictions for the first gear issue?

 

[gsxr]

Since the fuse was blowing previously, I'm suspicious of a wire shorted to ground somewhere in the circuit. I'd start at the transmission and work backwards. It's easy enough to check if the magnet/coil is shorted. Normal from center pin to ground is ~12 ohms. If it's like 1 or zero ohms, that might be the problem. This would be unusual though.

 

[Mikeg02222]

Since the fuse was blowing previously, I'm suspicious of a wire shorted to ground somewhere in the circuit. I'd start at the transmission and work backwards. It's easy enough to check if the magnet/coil is shorted. Normal from center pin to ground is ~12 ohms. If it's like 1 or zero ohms, that might be the problem. This would be unusual though.

View attachment 136140

Ok. I’ve got a multimeter so I’ll start with that and then start prodding around that diagram you sent me