• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

And the GMTDScanner Says

youll always get a stepper motor fault when your desired and actual/measured timing are not with a degree or so. Caused by the over advance, because the "base timing" is higher than the PCM's desired timing.

once the IP is turned so that the stepper can control timing like the PCM program wants, you wont get that code.
 
buddy said:
youll always get a stepper motor fault when your desired and actual/measured timing are not with a degree or so. Caused by the over advance, because the "base timing" is higher than the PCM's desired timing.

once the IP is turned so that the stepper can control timing like the PCM program wants, you wont get that code.
Click to expand...

Thanks. So you're confirming that all of my issues are related to my base timing being off. If/when I am able to address that, then all of this should go away. I'll have another go at it next weekend.
 
OK revisited this after leaving the batteries disconnected for a week. New battery (free from Sears) installed on driver's side. Moved IP as far to the passenger side as I could. Probably a 1/4" gap or more between my scribe mark and the chisel mark on the housing. Very hard to start. Tons of white smoke. Revv'd engine to warm up to 180. Rough running at RPMs above 2000. Codes were cleared from memory.:thumbsup: Actual timing was 13, so some improvement, but no where near the 4 degrees I've been told to look for. Could not do a Time Set or TDC Learn. Same codes: 88 and 34.

So, after going through the internal timing set twice now and posting photos here verifying the last effort. I'm still thinking the timing is off internally. Could the IP be off 180? Again, I'm lost on this and extremely frustrated.:nonod:
 
maybe you moved it too far 1/4" is alot. Also I went back and looked at your pics on timing chain. There is no pic of the ip gear but you should have rotated the engine until the dot on the cam gear pointed up and then the ip gear dot should be pointed down just like the timing chain and gear was. Also did you inspect the keys to see if they were sheared or partially sheared?
 
ak diesel driver said:
maybe you moved it too far 1/4" is alot. Also I went back and looked at your pics on timing chain. There is no pic of the ip gear but you should have rotated the engine until the dot on the cam gear pointed up and then the ip gear dot should be pointed down just like the timing chain and gear was. Also did you inspect the keys to see if they were sheared or partially sheared?
Click to expand...

Yes I rotated the engine until the dot on the cam gear was at 12 o'clock and installed the IP gear so that it was pointed down and lined up with the cam gear. No the keys were not sheared or even partially sheared.

I rotated the IP over that far because it was suggested that I needed to get actual timing down to below 4. At 13 it's lower than before (16), but no where near 4. Have not been successful at any IP position between this and all the way to the driver's side.
 
Please understand that this truck was running perfectly fine before I started the cooling upgrade and changing out the timing chain in the process. I'm having a hard time accepting that the PCM failed, or my IP failed, or the stepper motor failed, etc. Trying to focus on that I did touch in this work.
 
Here is a snapshot of one of my old trucks.

ENGINE SENSORS
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Engine run time: 00:14:07
Boost pressure (MAP): 13.81 PSI
Desired EGR: 15.23 PSI
Desired idle: 656 RPM
EGR pressure: 14 PSI
EGR duty cycle: 0 %
Engine coolant temp: 190.1 F°
Engine speed: 656 RPM
Glow plug relay feedback: 0 Volts
Glow plug voltage: 0.1 Volts
Ignition voltage: 13.6 Volts
Wastegate duty cycle: 87.1 %

__________________________________________________________________
INFORMATION SENSORS
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
PCM Calibration ID: 4735
Current DTCs: 0
Accel. ped. pos. 1: 0.69 Volts
Accel. ped. pos. 2: 4.35 Volts
Accel. ped. pos. 3: 4.02 Volts
Barometric pressure (BARO): 13.13 PSI
Battery voltage: 13.4 Volts
Fuel temperature: 108.9 F°
Intake air temp: 107 F°
Throttle position: 0 %
Turbo boost (Calculated): 0.68 PSI
Voltage reference sensor: 1.3 Volts

__________________________________________________________________
INJECTION PUMP SENSORS
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Actual injection pump timing: 33.18 Deg °
Cam reference missed: 0 Counts
Crank reference missed: 0 Counts
Fuel calibration: 95 Counts
Fuel rate: 7.5 mm³
Fuel rate - Cruise: 0 mm³
Fuel rate - Idle: 7.5 mm³
Fuel rate - Maximum transient: 68.75 mm³
Fuel rate - Throttle requested: 0 mm³
Injection pulse width: 1.86 ms
Injection timing - Measured: 11 Deg °
Injection timing - Desired: 10.9 Deg °
TDC offset: -0.62 Deg °

__________________________________________________________________
TRANSMISSION SENSORS
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
3-2 PWM solenoid duty cycle: 0 %
Cruise target speed: 0 MPH
Cruise speed error: 0 MPH
Current gear of transmission: 1 Gear
Current torque signal pressure: 31 PSI
Current transmission ratio: 1:4 Ratio
Error between desired and actual shift times for latest 1-2 upshift: 0.42 Sec
Error between desired and actual shift times for latest 2-3 upshift: 0 Sec
Force motor (PCS) - Duty cycle: 34.4 %
Force motor (PCS) - Feedback current: 0.64 Amps
Force motor (PCS) - Reference current: 0.62 Amps
Time of latest 1-2 upshift: 0 Sec
Time of latest 2-3 upshift: 0 Sec
TCC PWM solenoid duty cycle: 0 %
TCC slippage: -21 RPM
Transmission input speed: 679 RPM
Transmission output speed: 0 RPM
Transmission temperature: 146.3 F°
Turbine speed: 679 RPM
Vehicle speed: 0 MPH



Are you running a chip that isn't in your sig? Note my IP timing degrees....desired and actual at idle...


Again, ensure that your stepper motor is operating properly...
 
Chris, how did you get the scans posted?

It's the stock chip. Never been removed. I think it's located in the glove box?

I can barely see the stepper motor, let alone observe it work. I'm doing this work solo, so it's impossible to rev the engine and observe the stepper motor, even if I could see it.
 
Highlight the text in the gmtdscanner and press ctrl+c to cut...

Press ctrl+v to paste...

No friends? Relatives? Neighbors?
 
Dont be concerned with what they say at idle, only with what they are during timeset. It may be confusing to try to correlate whats timing during operation being controlled by the PCM and when trying to set the base timing and TDCO.

In Chris' screenshot you can compare desired and measured to the desired and acutal in timeset screen. Although while not in timeset mode that is based on coolant temp and RPMs, not good for comparing to timeset.

In order to help we need to know how far is as far as you could move it.
 
Here's a photo:

IMG_0856.jpg


The big scratch that's reflecting/shining is the chisel mark on the timing cover. Well the chisel mark is in the middle of that. Above it and to the left about an 1/8th inch or so in the black blob is the scribe mark I made which lined up with the chisel mark before I removed the timing cover the first time. When those two marks are in alignment, the IP is rotated towards the driver's side about as far as it will go. The fuel shut off solenoid is vertical. I have tried many positions between this and all the way to driver's side and seen little difference on the GMTDScan. The more I go towards driver, the higher the actual timing.
 
I went out and ran it again. Moved the IP pump towards the driver's side, as that is where it runs the best. I then had my wife rev the engine while I observed what I think is the stepper motor. I was watching a black cylinder with a horizontal electrical plug on top; it's located on the passenger side of the IP below the intake and towards the firewall from the timing marks in the prior photo. It has the diameter of a 50 cent piece and is about two knuckle high. There is nothing on this cylinder that can move and indeed there was no movement.

I scrolled through the GMTDScan software and the only place I could find the sensor listings that Chris showed is in a drop down at the bottom of the dash tool, but no numbers show up there in the listing. There's nothing to click on in the drop down. These do not appear in any of the other tools.
 
Last edited:
In the dashboard screen top right of the screen there is a Take a Snapshot. That is where Chris' data came from. Then in under the File you can click view snapshot. Cut and paste from that,
 
No I haven't read this specifically. Interesting read and and a good description. My answers to each point are in red.

Procedure for TIMESET and TDCO LEARN

--------------------------------------------------------------------------------
NOTE - these procedures are for the TECHX series of OBD1 scantools, but do work with the GMTDScan pcware.

Please post any differences you may encounter, for comment\enlightenment by the pcware author.

<><><><><><><><><><><><><><><><><><><><><><><><><> <><><><><><><><><><><><>

Make sure the ECT is above 180deg, BEFORE you do anything else

Done.

Make sure there are no stored DTC errors, BEFORE you do anything else

Done.

Read the AS-IS Des\Act timing, BEFORE you do anything else - make sure Act = Des, write them down

Did this, but Des has never = Act. It has always been off ranging from 15 to 5 degrees, depending on IP position.

Read the as-is TDCO, BEFORE you do anything else - write it down.

95% of the time it has been - 2.02; the other 5% it has (briefly) been 0.

If as-is TDCO is at -0.5deg, as-is Des\Act timing should be +3.5deg, also.

I wish

If so, rotate the IP 2 silly millimeters towards the driver's-side, snug it down.

Been there, done that.

Engine Coolant Temperature must be above 180deg F to continue, with no stored DTC's

Done.

Command TIME SET, idle will increase to 1000rpm, timing will go to 0, engine will sound labored.

Done. Idle has never increased, PERIOD!

Desired timing will = 0deg

Yes seen that.

Actual timing will = varying between +3.5deg and +5~6deg

Never. Range has flickered between +12 and +22, depending on IP position.

Exit TIME SET - normal idle will resume.

Done that. Idle never changed. When coolant is 180 F, idle is about 560 rpm.

Note Des\Act timing in degrees - both should be +8.5deg

I wish.

Command TDC OFFSET LEARN, displayed number will change to -1.5deg.

Done that. I wish.

This can be increased to -1.94deg by increasing rpm to some point above idle,
but below 1700rpm, where PCM will set the DTC

If I got to this point, I'd be dancing.

Exit TDCO LEARN, rattle will audibly increase, indicating advanced timing.

Go to Engine Data Display screens, read Des\Act Timing and TDCO.

NOTICE, here - this is for a '94-'95 OBD-I vehicle - TIME SET is specifically an OBD-I function.

If all is good, snug all 3 IP nuts down, take vehicle for a spin so PCM will store new driveability parameters based on advanced timing.

<><><><><><><><><><><><><><><><><><><><><><>><><>< ><><><><><><><><><><><>


Use this link for DS4 reference - http://fsunw3.ferris.edu/~millerm/SW...22 sensor"


TIMESET routine allows PCM to determine actual position of Inj Pump relative to crankshaft Top Dead Center, based on CPS output.
When you command TIMESET, PCM commands the TSM to rotate the OPTIC SENSOR to 0deg, which will be the maximum retarded position allowed by Inj Pump's fixed position, so DESIRED timing is 0deg, and ACTUAL, or MEASURED, timing is the physical IP position in degrees, which is then stored in memory when you exit TIMESET - this number is what I term 'Base Timing'.

Each time the engine is started, PCM compares CPS and IP position against the stored Base Timing values from the previous 50 starts to see if anything has changed, such as timing chain wear, or sticking TSM, so PCM can correct for minor changes over time, or set a DTC.

If nothing has been changed, or altered, or rotated, a commanded TIMESET event will be rather uneventful, as nothing will change - PCM will use and store the same numbers.

If IP has been moved, TIMESET causes PCM to stroke the TSM to full retard, notes the difference, then strokes the TSM thru it's full 11deg (IP) advance\retard movement, then again to full retard to determine the new position - this is where you will hear very harsh rattle and rough running for a few seconds, and rpm will increase to prevent engine dying as TSM strokes thru the entire newly-available timing range.

Does TSM = Timing Stepper Motor? Regardless, this has never occurred during Time Set. Nothing ever changes or happens to the engine during Time Set.

This also occurs with a replacement blank PCM, one with no previous data, or which has been 'wiped'.

TDCO is a calculated value based on the Base Timing number measured in TIMESET and stored in memory.
When you command TDCO LEARN, PCM compares the original TDCO value to the new Base Timing value, again strokes the TCM thru it's limits to find the total range of advance available to the Optic SENSOR, then calculates a new TDCO value based on the new upper limit of advance, which is then stored when you exit TDCO LEARN.

Example: Base Timing at +3.5deg with +14.5deg max advance, TDCO is -0.5deg

If Base Timing is advanced to +8.5deg, max advance is +19.5deg, and TDCO is -1.5deg to -1.94deg

Advance goes negative with respect to base timing only in TIMESET, when PCM DESIRES 0deg in order to MEASURE ACTUAL degrees, and TDCO LEARN, where PCM is determining new range of advance.
 
Last edited:
Yeah, that idle increases stuff doesnt apply to OBD1 trucks.

Is your coolant temp sensor stuff fixed? I'd hate to have cold advance stuff interfering with the attempt at setting timing.

What does GMTDScanTech say the temp is when running the timeset? It needs to thing its over 172 degrees otherwise the PCM may be advancing the timing.
 
Put in new coolant temp sender last week and it's working fine. I started the scan yesterday (twice) once the temp reach above 180. I need to pull that data screen that Chris posted as I want to verify the CPS is working from the crank count measure. It's either the CPS, or I still have the internal timing set incorrectly. I refuse to believe the IP or Timing Stepper Motor or PCM went out when they were fine before I started this job. The fact that my actual timing is nowhere near the specs suggested in the post above suggests that something is off. This should not be any more difficult than timing a distributor on a gasser.
 
"Does TSM = Timing Stepper Motor? Regardless, this has never occurred during Time Set. Nothing ever changes or happens to the engine during Time Set."


There is a connector right on the top of the stepper motor, is it connected?
 

Attachments

  • IP.jpg
    IP.jpg
    25.7 KB · Views: 11
You must log in or register to reply here.
Back
Top