# 2001 gmc 2500hd 8.1l **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** start\ **Created:** [August 28, 2014, 10:19am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858 "2014-08-28T10:19:02Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![dkello](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dkello/32/2891_2.png) [@dkello](https://community.cartalk.com/u/dkello)\ **Post date:** [August 28, 2014, 10:19am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/1 "2014-08-28T10:19:02Z")
Check engine light is on. Code reads CAM Sensor , however i changed out the sensor myself and it still wont go away. My truck wont start on the first two-three times and it will back fire occasionally. Any suggestions on what to do next? thanks ---
**Author:** ![jesmed1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jesmed1/32/2097_2.png) [@jesmed1](https://community.cartalk.com/u/jesmed1)\ **Post date:** [August 28, 2014, 8:58pm UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/2 "2014-08-28T20:58:49Z")
It’s possible the electrical connector itself is faulty. Try replacing the connector. It’s around $40 for the part. ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [August 28, 2014, 9:35pm UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/3 "2014-08-28T21:35:31Z")
Anytime you replace that you need to do a Crankshaft Sensor Variation Relearn. This is according to the GMC forum. ---
**Author:** ![dkello](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dkello/32/2891_2.png) [@dkello](https://community.cartalk.com/u/dkello)\ **Post date:** [August 29, 2014, 6:30am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/4 "2014-08-29T06:30:17Z")
knfenimore…do you have a link available so i an read more about the variation relearn? ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [August 29, 2014, 9:05pm UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/5 "2014-08-29T21:05:17Z")
[http://my.cardone.com/techdocs/PT%2070-77-0003.pdf](http://my.cardone.com/techdocs/PT%2070-77-0003.pdf) ---
**Author:** ![dkello](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dkello/32/2891_2.png) [@dkello](https://community.cartalk.com/u/dkello)\ **Post date:** [September 2, 2014, 3:11am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/6 "2014-09-02T03:11:03Z")
had a mechanic shop do the variation relearn and the code came back right after I left… ---
**Author:** ![jesmed1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jesmed1/32/2097_2.png) [@jesmed1](https://community.cartalk.com/u/jesmed1)\ **Post date:** [September 2, 2014, 4:29am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/7 "2014-09-02T04:29:00Z")
Check the connector. ---
**Author:** ![dkello](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dkello/32/2891_2.png) [@dkello](https://community.cartalk.com/u/dkello)\ **Post date:** [September 20, 2014, 10:58pm UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/8 "2014-09-20T22:58:49Z")
the code has cleared…still backfires and wont start on first attempt… ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [September 21, 2014, 12:00am UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/9 "2014-09-21T00:00:18Z")
Did you use an AC Delco cam sensor? Did you check the 5V reference and ground? Did you check that the new cam sensor is actually producing a signal? ---
**Author:** ![Jdm2500hd](https://avatars.discourse-cdn.com/v4/letter/j/35a633/32.png) [@Jdm2500hd](https://community.cartalk.com/u/Jdm2500hd)\ **Post date:** [March 19, 2017, 2:36pm UTC](https://community.cartalk.com/t/2001-gmc-2500hd-8-1l/86858/10 "2017-03-19T14:36:53Z")
Hi, I know this postime is a few years old but I have a 2001 2500hd 8.1l with the exact same issues. Did you ever get this problem resolved? If so what was it? I’ve changed the cam sensor twice, first sensor was a BTW brand I think and it gave off low input code, second sensor was ac Delco brand which gave off high input code. I left the ac Delco in and changed the crank sensor and did a relearn and still setting a engine code, doesn’t want to start right away, backfires sometimes. Pigtail seems fine