What P0798 means
Pressure control solenoids are current-controlled proportional valves, and what B and C mean depends on the design: on GM's clutch-to-clutch automatics they are the pressure valves of clutches 2 and 3, on GM's CVT B is primary pulley pressure and C line pressure, on Jatco CVTs B is the secondary pressure valve, on Saab's AF40 B and C are clutch valves SLC1/SLC2.
How the engine computer detects it
P0798 is the electrical code for valve C. Only Saab's 9-5 (2010–11) with Aisin AF40 uses it: a deviation between commanded and feedback current of clutch valve SLC2 (normal range 0.1–1.1 A), with the circuit codes P0969–P0971 alongside, rated after two trips. The module switches all solenoids off and keeps only second gear and reverse, without adaption. GM and Ford use the circuit codes P0968–P0971 instead.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Limp mode (second gear and reverse only)
- Harsh shifts
- Transmission warning or check engine light
Common causes
- Clutch valve SLC2 coil faulty Most likely
- Wire or connector open or shorted Possible
- Transmission module damaged (e.g. after a short) Less likely
How to diagnose P0798
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: pressure control solenoid, transmission valve body, transmission clutches, transmission control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 7
- Transmission
- 98
- Specific fault
Questions drivers ask
Can I drive with code P0798?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0798?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0798 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.