Worn switch contacts and leaking switch seals or replacement seals that are too thick.
Replace worn diaphragm and switch contact with the properly dimensioned parts.
The 41TE and 42LE solenoid packs are easy to rebuild. Getting parts that work is another story. Often times, the brass switch contacts bind in the housing bore, or the switch diaphragms are too thick to allow proper switch operation. These problems are often the cause of switch codes and continuous limp-in complaints. The Sonnax rubber diaphragms match OE specifications, and the switch contacts are specially dimensioned to prevent false/intermittent switch codes. It is no longer necessary to purchase a solenoid pack from the dealer just to get the right contacts and diaphragms.
Contact a Sonnax Parts Distributor.