Shifting Problem

[jwr870sx]

I have a 97 gt w/3800 engine. I was cruzin' down the highway last night at 70 mph not getting on it or anything. all of a sudden the car shifted out of O.D. into drive and ses light came on. I let off of the accelerator and the r's dropped to idle speed. Stopped car and started up again, car did not shift down, stayed in 3rd. Manually shifted ok but still didn't go into O.D. Stopped car again shut it off and every thing worked normal???? Can anyone tell me what is up?

[jessep28]

Since the SES light came on, you can take the car to Autozone and they will usually scan it for you. Get the codes, resist any parts sales pitches and bring them here and the guru's here will tell you the possible causes.

I would also consider taking it to a transmission shop and they will run a diagnostic for you.

[jwr870sx]

Thanx, I will set up a diagnostic tomorrow and get back with the codes

[jwr870sx]

The code is 502 speed sensor low voltage. The guy who pulled the codes said to clean the plug in to start with than go from there.

[BNaylor]

Originally Posted by jwr870sx

The code is 502 speed sensor low voltage. The guy who pulled the codes said to clean the plug in to start with than go from there.

Tranny DTC error code P0502 is vehicle speed sensor (VSS) circuit (low input). The sensor is a permanent magnet generator mounted to the transaxle case extension. It feeds the PCM to determine shift timing, TCC (torque convertor) apply and release, and gear ratio calculations. The PCM will receive and process the AC voltage and convert it to digital.

You can start by cleaning the electrical connector plug. If that doesn't work you can check the resistance and voltages with a multimeter.

VSS resistance = 981 - 1864 ohms
VSS voltage = .5 volts AC at 100 rpm to more than 100 volts AC at 6000 rpm

BTW - To check output voltages the engine must be running and transaxle/wheels must be turning. Not an easy job in this respect.

Good luck!





Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[regalfriend]

i had similar problem....low voltage...i lost 4th gear and lockup...the ECU was checked and found no malfunctions. Turns out turbine speed sensor was replaced and voltage came up...I dont know if TSS will effect voltage but know that voltage did come up after repair