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.

STATUS FLAGS THAT WERE SET/CHECKMARKED

With cold engine at IDLE

IOD port A:
Stepper motor inhibit - Run/inhibit
EGR vent enable - on/off
Force motor enable - on/off

IOD SOD status register:
Coolant temp pull-up select - on/off
Trans temp pull-up select - on /off

TCC mode word 2:
Min. threshold occurred

With cold engine at CRUISING speed

IOD port A:
Use hyst. for vehicle speed

With warm engine at IDLE

TCC mode word 2:
Perform apply
TCC bus is valid
Delay is in progress

With warm engine at IDLE:
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

[trdwlr]

yeah I wouldalso like to know what that all means

[gmctd]

My apologies, piersbc - I could have sworn I replied to your post.

Not sure what the stuff at the top is, but here's the rest -

With warm engine at IDLE:
Desired injection timing = +6.2 degrees
This is the timing the PCM is calling for in deg BTDC, based on the actual position of the Inj Pump

Actual injection timing = +6.4 deg
This is the measured position of the Optic Sensor in deg, having responded to the Timing Stepper Motor input from Desired injection timing - Des\Act should be within a degree or so if IP is functional

TDC offset = -1.85deg
This is a calculated value, based on the actual position of the Inj Pump in deg BTDC - the greater the initial advance, the greater the negative value
__________________________ ________________________ _______________

-------------------------------------IDLE-------Acceleration ----CRUISE
Turbo Boost -------------------------.8 psi ----- 8 psi -------- 5 psi
Boost is normal for those conditions - reason you're seeing Boost at idle is because the MAP or\and Baro sensors do not agree, or you're at high altitude

Boost pressure ----------------------14psi--------39 psi -------- 20psi
Boost is in psia, so subtract measured Barometric pressure at idle - 14psi, here - from those values
Low measured Baro could indicate faulty sensor, or dirty air filter in S engines, as they use the MAP sensor for Baro

Waste gate duty cycle ---------------73.4 %------64.5% -------- 59%
This is normal, as PCM digitally regulates vacuum applied to the wastegate - 100% is full 25" for full Boost
____________________________
Fuel Rate----------------------------9mm--------33.19mm ------24mm
Those Fuel rates are normal for those conditions - that's the quantity demanded by the APP input (driver)

Measured injection timing ------------5 deg ------7 deg ---------7 deg
This is the actual position of the Optic Sensor, is degrees advance, BTDC, and should compare closely to Desired injection timing - dunno about these particular figures, I'll check it out with mine

Injection Pulse Width----------------1.8 ms-------1.9 ms---------1.9ms
This definition is ambiguous in OBD1, but should be the time it takes the Fuel Solenoid to close, starting the injection event - still trying to figger this one out

Fuel Pump Timing -------------------27deg -------30 deg---------29 deg
Unknown at this time

Max transient fuel rate--------------42.5mm------62mm---------56mm
Unknown at this time
____________________________
Desired EGR--------------------------11.6psi-----15.23 psi ----- 11 psi
EGR actually measures applied vacuum, which is any pressure lower than Baro - this is PCM demand based on driving conditions - if you have the F engine, no EGR, PCM still does the calculations

EGR pressure -----------------------11.6psi------14 psi ---------18 psi
EGR is measured vacuum, read by the sensor on the firewall with the S engine

EGR Duty Cycle---------------------53%---------0 % ---------- 40 %
PCM digitally regulates vacuum applied to the EGR to open the valve, similar to the WG solenoid
______________________________
The following are transmission data -

These are transmission line pressure - PCM pulses the line pressure valve to full output every few minutes to prevent the valve sticking in the bore

Current torque signal pressure-------25psi--------50 psi-------- 27psi
This is the regulated line pressure in the 4l80E - greater engine input requires more pressure

Force motor Reference current pcs---.82amp------.64amps------.8amps
PCM digitally regulates line pressure - this is PCM desired current

Force motor Feedback Current pcs---.82amp------.8amps------- .78 amps
This is Measured current - should be close to Reference current, could indicate solenoid problems or poor connections, or PCM was pulsing to full pressure at those readings

Force motor duty cycle--------------44.5 %-------43%----------43%
This indicates the percentage of digital power applied for regulation
________________________________
These two are the Torque Convertor Clutch apply force -

TCC PWM Solenoid duty cycle--------0 %----------80%----------6.2%
PCM digitally regulates oil pressure to the TCC clutch - this is the percentage of digital power applied - cruise should be 76-86 %
6.2% would be a lot of slippage - compare it to idle TCC apply of 0% pressure

Amount of TCC Slippage-------------40 rpm-------800 rpm-------2 rpm
This is comparing turbine input rpm, which is engine rpm, to Input speed sensor rpm - you were getting good efficiency at cruise with only 2rpm loss, which should indicate the duty cycle was actually higher than your posted reading
Or this 2rpm value was incorrect
__________________________________________________ __________________________________________

Again, not sure what happened here, as I thought I responded shortly after you posted.

They say two things start to go as someone gets older - one is health, but I can't remember the other thing..............

[piersbc]

gmctd...actually you did respond back in Febuary...I don't know what happened to the posts though. But thanks for this in-depth explanation. It will help me keep my rig running for another 10 yrs.....(fingers crossed)