Finally fixed DTC 35

[sbigos]

At least I think it's fixed. I found that my boost sensor mounted on the very top of the air plenum leading into the intake manifold was loose, one bolt completely out and laying in the intake valley, the other only holding by a few threads and the sensor flopping around. I think when the IP was replaced about a year ago they must not have tightened those two bolts. I can't see any connection between DTC 35 and bad boost sensing though.

After about 60 miles now, no more DTC 35 which I used to get about every 5 miles. I also cleared all stored codes by disconnecting the battery, and I made the mod to make the lift pump run during glow plug activation, which couldn't have anything to do with DTC 35 I think.

Still need to fix my hard starting which I am now thinking is due to a timing change when the IP was replaced.

Can anyone say if once a DTC is set does it keep repeating or just set once and go away? When I got a DTC every few miles, was it repeating the same error or resording new ones. Thanks.

[ucdavis]

DTCs generally have a set of "conditions" to cause the computer to set them, and clear once clean operation w/out the conditions occurs for a given number of starts, or warm-up cycles happen.
But... more than one GM tech has told me that multiple DTCs can mean that one or more of them is the real trouble and the PCM is reading the overall operating trouble as sveral DTCs (i.e. you can get a smorgasbord of DTCs, some of which are fake). I have found this to be true on more than one occasion.

[gmctd]

DTC-35 is Inj Pulse Width Short - air bubbles in fuel will set this code.
Can be caused by inadequate fuel supply to Inj pump - clogged filter, low volts to lift pump, plugged fuel line, etc.
Possible your wiring rework to the lift pump cured it.

Loose Boost Sensor can cause DTC-78 or -61.