4.3 AFM Vibration - TSB number?

[14silverado4.3]

I have seen a TSB a while ago for exhaust ground out condition. Anyone know the number?

[tbarn]

THIS ONE?

 

#PIP5228A: Vibration During Active Fuel Management V4 Mode Operation 1200 – 1400 Engine RPM - (Oct 22, 2014)
Subject: Vibration During Active Fuel Management V4 Mode Operation 1200 – 1400 Engine RPM

Models: 2014-2015 Chevrolet Silverado
2014-2015 GMC Sierra
equipped with 4.3L RPO LV3

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This PI was superseded to update Cab Mount Settling Procedure. Please discard PIP5228.

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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some customers may comment about a vibration that is felt between 1200 – 1400 engine RPM when in active fuel management V4 mode. A drone or resonance may also accompany this vibration. The vibration may occur at different vehicle speeds but the engine speed will be in the 1200-1400 RPM range. This vibration does not occur in V6 mode.

Recommendation/Instructions
The technician should evaluate the vehicle under the conditions the customer duplicates the concern. Once the concern is duplicated, use a vibration analysis tool, J 38792-A Electronic Vibration Analyzer 2 (EVA) or CH 51450-NVH Pico Oscilloscope Diagnostic Kit (w/NVH) to measure the frequency of the vibration. If the measured vibration is not 23 Hertz (HZ), first order engine, use normal vibration diagnostics to isolate the source of the vibration. If the measured vibration is 23 Hertz (HZ), first order engine, follow the three-way catalytic converter and cab mount settling procedures below

Three-Way Catalytic Converter Assembly Settling Procedure
Note: Do NOT replace the three-way catalytic converter assembly unless it is physically damaged.

Loosen the six nuts that fasten the three-way catalytic converter assembly to the exhaust manifolds.

Remove and replace the exhaust muffler clamp that joins the three-way catalytic converter assembly to the pipe of the muffler assembly. Note: This is a special clamp called a Norma clamp and it must be replaced as it is a one time use clamp.

Reinstall the three-way catalytic converter assembly following the specific tightening sequence and fastener torque specifications found in SI.

Cab Mount Settling Procedure
Warning: When settling the body cushions, do NOT separate the frame from the body more than is necessary. Possible personal injury and damage to multiple parts may result if you do not follow the guides outlined below:

Intermediate steering shaft—Do not allow the shaft to extend more than 25 mm (1 in).

Fuel tank filler hose—Do not stretch the hose excessively.

Tail/Turn signal lamp wiring/rear lamps junction block—Leave slack in the wires

Park brake cable—Leave slack in the cable.

Body ground straps—Leave slack in the wire

The technician should first loosen the fastener located at the center of each body mount (6 for a regular cab, 8 for crew and double cab).

Using a large angled pry bar, lift up the cab body slightly to settle / relax it. Perform this at each mount location one at a time.

Repeat this cab mount settling process twice, to confirm the mounts are settled / relaxed.

Visually verify that the cab to box alignment is correct before re-torquing all mounts to specification found in Service Information, body repair, frame and under body section.

[14silverado4.3]

Yep that is it

[14silverado4.3]

What does the PI stand for? Are these TSB's?

[fondupot]

PI is "Preliminary Information" which is an unpublished bulletin (TSB). Which means only GM service personnel can see it.

[tbarn]

fonduot is correct. A of today, there 11 technical service bulletins and about 90 information bulletins. About 250 Preliminary information bulletins or "PI's". Some PI's are later re-released as TSB's but only a small percentage . FYI , information bulletins are usually worthless .

[GMMediumDutyMQ]

Good luck using this to get anything resolved. I've had my truck in twice, each time bringing the PI document IN HAND to my service rep. While they fixed a cracked exhaust on the first try (which did reduce the drone), the underlying shimmy still exists. I have no idea what the hell they're doing in the shop, or why they at least wouldn't try doing what's listed in the damned document.

[steveos3312]

This bulletin describes my issue to a tee.

 

Has anyone had any luck getting this resolved based on this procedure? It sounds like the dealers/shops have their own agenda on fixing this but its been a while since last post. Curious if any luck here or elsewhere. Thanks.