OBDC II Codes P0251 and 0370

[bmwdan42]

Have a new to me '97 2500 SLE GMC, 6.5L Auto with 149k miles Prev owner put rebuilt inj pump on. Truck runs just fine, but gives those two codes. I've erased them several times but they return upon starting the truck. Any hints?
Thanks in advance.
Dan

[joed]

I'll take a stab...

P0251 is Injection Pump Cam System
P0370 is Timing Resolution High Reference

I believe both have to do with the optical sensor on top of the injection pump. Troubleshooting for these is rather involved (according to my online service manual) - it has you check for proper voltage, connections to both the PCM and optical sensor. They could indicate a bad wiring connection, bad PCM, or bad injection pump (its optical sensor).

I think most that have had these codes end up replacing the injection pump...

The troubleshooting does say that these codes can be caused by air in the fuel system, so it's worth while to check your fuel filter and your lift pump's operation first.

Hope that helps.

Joe.