Having problems with your 2001 Chevrolet Silverado ?
Transmission will not shift out of low on my chevy 2001 3500 , the code is p0700 and p1781, p1721
P0700 will come up with most all codes or faults to do with a transmission,P1781 is 4X4 switch out of range,I have never heard of a P1721 but a P0721 is trans output sensor range or performance.If the computer isn't getting a output speed it doesn't know that it should shift.I would check all your wiring down around the trans area looking for broken or grounded wires if ok have the speed sensor checked for being opened.
Repair Help & Product Troubleshooting for 2001 Chevrolet Silverado
Tips for a great answer:- Provide details, support with references or personal experience .
- If you need clarification, ask it in the comment box .
- It's 100% free, no registration required.