GMTDScan diagnostics

[piersbc]

I ran a bunch of test this weekend on my truck with the GMTDScan software and here are the results....please let me know if any of the figures are out of spec.

Desired injection timing = 6.2 degrees
Actual injection timing = 6.4 deg
TDC offset = -1.85
__________________________________________________ ______________

-------------------------------------IDLE-------Acceleration ----CRUISE
Turbo Boost -------------------------.8 psi ----- 8 psi -------- 5 psi
Boost pressure ----------------------14psi--------39 psi -------- 20psi
Desired EGR--------------------------11.6psi-----15.23 psi ----- 11 psi
Waste gate duty cycle ---------------73.4 %------64.5% -------- 59%
Fuel Rate----------------------------9mm--------33.19mm ------24mm
EGR pressure -----------------------11.6psi------14 psi ---------18 psi
Measured injection timing ------------5 deg ------7 deg ---------7 deg
Fuel Pump Timing -------------------27deg -------30 deg---------29 deg
Injection Pulse Width----------------1.8 ms-------1.9 ms---------1.9ms
EGR Duty Cycle---------------------53%---------0 % ---------- 40 %
Max transient fuel rate--------------42.5mm------62mm---------56mm
Current torque sign al pressure-------25psi--------50 psi-------- 27psi
Force motor Reference current pcs---.82amp------.64amps------.8amps
Force motor Feedback Current pcs---.82amp------.8amps------- .78 amps
Force motor duty cycle--------------44.5 %-------43%----------43%
TCC PWM Solenoid duty cycle--------0 %----------80%----------6.2%
Amount of TCC Slippage-------------40 rpm-------800 rpm-------2 rpm

[gmctd]

Those mostly appear ok - EGR is not required unless you have a 1500 or Kalifornia emissions.

Inj Pulse Width is a little long at 1.9ms - check Ignition Voltage, and see what it does in warmer climes.

Watch ECT, Fuel Temp (internal to the IP), and IAT when monitoring higher Boost pressures, along with EGT if you have a pyrometer.

TDCO is good, but Des\Meas IP timing seems a little low - PCM Desires IP advance, commands the TSM to provide that advance, Measures the resultant advance via the Optic Sensor - all referenced to the actual position of the Inj Pump.

The data will become familiar as you use the scanner, and you can easily spot irregularities with potential for DTC

[piersbc]

Thanks for the reply....if the Des\Meas IP timing seems a little low is there something to do about it? I see the GMTDScan software has the "learn" feature.

And is there a way to adjust the inj pulse width? They are the original injectors with 153,000 miles on them.

[gmctd]

Injector PW is set by the PCM - response is determined by battery voltage, Inj Pump condition, Fuel Solenoid response, fuel viscosity\quality, ground quality.

That is an Inj Pump parameter - other than those variables, there is no owner-accessible adjustment.

Injectors set injection pressure and the spray pattern, so you should pull those hi-milage injectors and have them tested.

Had IP timing been previously adjusted to achieve the -1.86deg TDCO?

[piersbc]

Thanks gmctd....I guess it's time to put on new battery cables and check my grounds and get some new injectors. I had a new IP put on about 2 yrs ago and I had them set the TDCO to as close to -1.95 as he could.

[gmctd]

I'd take a look at the cables and stuff first, try a clean-up, add Dr Lee's battery-post fix - if the cables are corroded, then it's time for new ones.

Clean the PCM harness grounds at the back of the engine, etc.

The Inj PW should drop to 1.85ms or so after the engine bay clean-up - could also be a good check for early IGN switch failure, as carboned contacts would cause the same symptom.