P0502, P0401

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Hello,
I have a 00' LS, and recently, it's hesitant to go into 1st gear (auto trans.) I have to rev the engine before it sputters into 1st. I told a mechanic who thinks it's a transmission, but I took it to autozone, and received 2 codes; P0502, & P0401. I heard GM makes a transmission that is compatible, which way is best??

[amigo-2k]

What is the history on your fluid changes?

This could be due to a dirty trans selector or low tranny fluid or a weak battery/alt. Isuzu's do funny things with weak electrical systems.

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Originally Posted by amigo-2k

What is the history on your fluid changes?

This could be due to a dirty trans selector or low tranny fluid or a weak battery/alt. Isuzu's do funny things with weak electrical systems.

-Thanks, really appreciate your reply. Truth told, no tranny fluid change since my possession 12/01/06, but I'm going to have someone look at the truck later this week. New battery since Jun '07. I took it to a mechanic previously for a different issue (key not coming out of ignition). They told me the shifter cable needed to be replaced; could this be possibly related?

[Gizmo42]

P0502 is vehicle speed sensor, low input. I've had this a few times on mine but only while offroading and climbing uphill really slow. I always just clear the code and it stays away.

P0401 is EGR system insufficiant flow. Wont effect the transmission but you should get the EGR system serviced. Clean the egr valve as well as the tube that goes inside the intake http://isuzufaq.ibctech.ca/#faq1

I'm thinking the shifting problem is either the range mode sensor needing cleaned http://forum.planetisuzoo.com/viewtopic.php?t=1707 or bad/burnt fluid which need changed. Just have the pans dropped and filter replaced along with whatever fluid comes out. It wont replace all the fluid, but its a start. With unknown service history DO NOT get the trans flushed. That usually kills them.

And, the transmission IS a gm. Its a GM 4L30E. They were also used in BMW, Cadillac, etc. But they are not identical so wont swap.