On the way home today, CHECK ENGINE light came on. Then a experienced a surging idle and intermitant tach signal. Plugged in code reader (Actron CP9180 and it can not establish communications with vehicle. I stopped by and tried another code reader and got the same results.What next?

Double check the wiring in the OBDII port...

Disconnected the battteries, removed and cleaned all fuses/relays withh contact cleanr; no codes ths morning

Was your scanner able to comunicate with the truck?

Was your scanner able to comunicate with the truck?

Still no communication with the truck thru the DLC

--- Update to the previous post...

Went to the beach for the weekend, but before i left i picked up some backprobes for the multimeter so i can test Sunday

Harness is good in regards to the DLC pinout. Unwrappped the harness and rewrapped it. have not figurd out what signals i sould be getting at the DLC

Just got done testing. At the DLC Connector: Pin 3 0.02 V Pin 4 Open, traced to DLC Connector using ECT2000 (Power Probe short chaser) Pin 5: Good Ground Pin 6: 4.98V Pin 7: 4.98 V Pin 11: 2.43 V Pin 14: 4.29V Pin 16 12V Will back trace Pin 4 from G200 Ground termination to DLC Connector to verify problem is the terminal in the DLC.

Here are the values After I fixed the ground open on pin 4

Check Engine Light came on again, unnablle to connect tto vehhicle.. does anyone have a good set of reference values at tthe DLC connctor i can compare to?

Anyone?

You got a problem on that leg of the CCD network it show be roughly 2.4-2.5 volts. So double check and make sure there is no other shorts... Might be a damaged device (Overhead console, radio, etc.)

Driving down the road today at 45mph, 16psi fuel pressure: Lost tach, CEL came on and engine cycled between 600 and 1200 rpm. Pulled over and tach came back, engine smoothed out and idled normally. Still unable to connect with code reader.All overhead console functions are working.Radio WorksPulled abs plugs and still got same voltage to Pin 4

Sound like a loose connection or a short to ground somewhere.

ll, keeps getting worse, Now I loose tach signal and the engine surges, Change the cam position sensor and still have the problem. looks like PCM time:mad:

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I had the idle issue in my truck for a couple of weeks off and on it finally threw a crank sensor code. I replaced it and problem has deceased since. When it my truck was idling at a stop light it would cut out for a split second and the tach would quit registering. Something maybe you could look at before you change out the expensive pcm.

Truck is running good now with a crank position sensor and another PCM; but still unable to read codes