1998 Saturn SC1 shifting problems

RICKFULLMER

MEMBER
1998 SATURN SC1
4 CYL
FWD
AUTOMATIC
11,500 MILES

When driving at highway speeds the car will shudder at 55 mph to 60 mph. It seems that it will not down shift from overdrive. I either shift through the gears from low to drive or I force the accelerator detent to come out of the hesitation. I suspect a torque converter solinoid having a problem. Also I have a check engine light with an O2 sensor problem. Scan code fault states cat converter efficency problem, but the exhaust pressure is good and the car runs good.

1 Reply

DAVE H

MECHANIC
13,384 POSTS

DESCRIPTION & OPERATION
Saturn vehicles use a 4-speed, fully automatic, electronically controlled transaxle with shift mode select function and self-diagnostic function.
The transaxle uses 5 electronic valves (line actuators), controlled by the Powertrain Control Module (PCM). The PCM controls all transaxle shifts, shift feel, Torque Converter Clutch (TCC) lock-up and self-diagnostics. PCM is located behind right side of dash. PCM has two 32-pin connectors and two 24-pin connectors.
If an electrical circuit or component problem occurs, MALFUNCTION INDICATOR LIGHT (MIL) may illuminate or start flashing. PCM will store Diagnostic Trouble Codes (DTC's) in memory. A stored DTC indicates PCM has detected a fault in engine or transaxle circuits or components.
PCM is capable of operating in 2 different modes. The differences between the 2 modes are shift points. NORMAL mode or PERFORMANCE mode may be selected using mode switch. Mode switch is located on center console.