: p1520 Trans Circuit

08-17-08, 08:22 PM
I've got a '97 SLS that was having trouble shifting the last time I drove it. I did a WOT to get to 80mph on the interstate, but then the rpms stayed at 3000+ when I started cruising like the overdrive never kicked in or it never shifted to 4th gear. The car continued to shutter and was having problems finding the proper gear. The SES light came on from code p1520 transmission range switch circuit. There are a lot of posts on here from people tripping that code, but there is very little about how to fix it or what the problem is. A couple people went to the dealership...is that my only option? Should I go to the dealership or a tranny shop? Can someone post about how/what they did to fix this issue?

08-19-08, 04:04 PM
Different question...where do you check/add transmission fluid?

08-19-08, 06:29 PM
The transmission dipstick is (standing in front of the car looking down into the engine compartment) on the right side of the engine assembly, down under parts of the intake tract and maybe an air intake resonator....not sure about your model.....The stick is a black twist cap with a red (?) line across the finger handle. Just right of the coolant crossover housing and upper hose outlet........

The 4T80E is a dry sump transmission: there will be no fluid on the stick with engine off, cold. The correct level is in the middle of the hot hashmark, engine running, hot, shift cycled through P-R-N-D and back several times, back to P and check.

If you have had no service done to the transmission recently, you can use either DEXRON-III or the new synthetic DEXRON-VI which is backwards-compatible. (GM TSB on this earlier this year.)

Exactly in the center of the pic.......

08-21-08, 10:42 AM
Great, thanks. Maybe I'm just a little low on fluid. I did notice a small amount of red fluid hanging on underneath the car when I changed the oil two weeks ago. I'll have to pull the air intake and check the dipstick.

08-21-08, 02:04 PM
So my fluid isn't low. Its brown and smells kinda burnt which probably isn't good, but the level is right in the middle of the dipstick. I guess I'll keep searching...

08-23-08, 11:11 AM
So to follow-up, it appears like I've got one of the P0741 Torque Converter Clutch problems. After I cleared the codes, this code was the only one that came back. I'm not exactly sure what I'm going to do now. I was thinking about selling the car, and while I'd only like to get about $3k for it, I think I'd be lucky to get $1500 with the idiot light on due to this problem. Too bad...this car seemed to not have headgasket problems or the previous owner had the engine replaced.

11-12-08, 11:26 AM
I'm dealing with the same issue on a 1999 DeVille. How exactly did you determine that you had a "P0471 Torque Converter Clutch" problem? Did your car show that code or did you take it to the dealer or a transmission shop or ???

I'm getting P1520 and P1527 codes, 4 times in the last 3 months, but no P0471. Also, the Service Engine light has never come on.