480LE transmision code 68

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#1
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MAKE:Chevy
MODEL:Silverado
YEAR:1993
MILES:96,000
ENGINE
:454
DESCRIBE ISSUE....

480LE transmission rebuilt $2,580 at professional shop due to loss of transmission oil from ruptured oil cooler line. Engine is immediately throwing codes 43 Knock Sensor and 68 Torque converter slipping. Transmission feels to be shifting fine and shop assures me that the converter is locked up as they tested this. I’m really not knowledgeable about transmissions. Is this maybe a speed sensor issue? Is this something to be concerned about?
 

nickb2

Wrench. Diagnostic Tech.
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#2
Common occurrence is in the passthrough round connector on tranny. Check to see if any corrosion, looseness, deformed pins. Check for oil intrusion, maybe that oil leak made it's way into the passthrough connector. Clean it and apply dielectric grease and make sure pins are tight.

My database tells me it is an overdrive ratio error/circuit. Here is a PDF of the flowchart for code 68. ACE 0. Here is also a flowchart pdf for code 48. ACE 1. Sadly the flow chart does not list much else to do if dtc is continuous and keeps coming back except to replace the BPVM(brake pressure modulator valve).

These are manufacturer codes, what type of scanner are you using? Most cheap code readers will not display these. Are you using a laptop or high end, or getting them read by a friend or a garage? I am just interested, always like to know what folks here use.
 

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#5
Common occurrence is in the passthrough round connector on tranny. Check to see if any corrosion, looseness, deformed pins. Check for oil intrusion, maybe that oil leak made it's way into the passthrough connector. Clean it and apply dielectric grease and make sure pins are tight.

My database tells me it is an overdrive ratio error/circuit. Here is a PDF of the flowchart for code 68. ACE 0. Here is also a flowchart pdf for code 48. ACE 1. Sadly the flow chart does not list much else to do if dtc is continuous and keeps coming back except to replace the BPVM(brake pressure modulator valve).

These are manufacturer codes, what type of scanner are you using? Most cheap code readers will not display these. Are you using a laptop or high end, or getting them read by a friend or a garage? I am just interested, always like to know what folks here use.

Thanks for the information. I'll suggest that the shop do the inspection for connectors etc. If found I'll credit you. One clarification is that the truck is a K3500. I am not 100% sure, but believe its only rear wheel ABS from experience driving and also I have never seen any sensors at the front wheels when doing brakes etc. As far as the codes I just read the codes from shorting the A&B leads and read the blinking check engine light. The shop that read the torque converter speed differential had a much more sophisticated setup. No idea what that was.
 
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#6
A wire was found disconnected to the knock sensor. when this was plugged back in both codes went away immediately. So not sure why the transmission slip code comes on with the knock sensor data wire out, but it does on this truck.