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Genuine GM NSBU Switch, Duramax & Gas | 2001-2004

ACDelco

$269.99
SKU:
19540535
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One of the most common problems with the Allison transmission on 2001-2004 GM Duramax diesel trucks is a failed NSBU switch. The NSBU is the Neutral Safety Back Up switch, and a failed switch can cause your truck not to start. This genuine GM switch (park/neutral position and backup lamp switch) is a direct replacement for 2001-early 2004 Chevy Silverado and GMC Sierra 2500HD and 3500HD trucks with the LB7 6.6L Duramax diesel, and it is also used on many 2001-2004 GM 2500 and 3500 gas trucks and SUVs.

Features

  • Genuine GM part 19540535
  • Direct replacement with OEM fit and finish
  • Solves a common problem with failing switches
  • Easy to install with common hand tools

What's Included

  • (1) Genuine GM NSBU switch

When to Replace

  • No start condition
  • Gear shift indicator on the dash not following properly, or a blank or flashing PRNDL display
  • Transmission stuck in limp mode or fail safe
  • Trouble codes indicating pressure switch manifold (PSM) faults

How Does a Duramax NSBU Switch Work?

The 2001-2004 Duramax trucks are equipped with a column shift selector. The neutral safety back up (NSBU) switch is another component associated with the column shifter, only it is mounted on the selector shaft of the transmission. Mounting directly on the transmission housing from the outside, the NSBU switch detects the angular position of the shift selector shaft and sends this position information to the transmission control module (TCM), so that certain vehicle control functions can be coordinated with the position of the shift controls. The neutral signal output of the NSBU switch is typically used as confirmation that the transmission is in neutral or park before the engine starter is engaged.

The reason PSM codes may set is that the NSBU switch and the internal PSM "look at each other" and "compare readings." The NSBU switch lets the TCM know which gear position you, the driver, have selected, while the PSM tells the TCM which gear the transmission is in based on hydraulic inputs. If the data from the PSM and the NSBU switch do not agree, trouble codes may set. The NSBU switch is subject to water contamination, which can cause it to give faulty readings.

Before You Order

Installation Tips

  • Place the shifter in neutral before removing the old switch, and install the new switch with the transmission still in neutral.
  • Inspect the connectors for water, corrosion or damage before plugging in the new switch.
  • Clear any stored codes after installation and confirm the gear indicator matches the shifter in every position.
  • Confirm the truck only starts in park and neutral, and the backup lights work in reverse.

Related Parts

Frequently Asked Questions

Is this a genuine GM part?
Yes. This is genuine GM part number 19540535.

Can a bad NSBU switch cause a no start?
Yes. The TCM uses the NSBU switch to confirm the transmission is in park or neutral before the starter is engaged, so a failed switch can prevent the truck from starting.

Why do I have pressure switch manifold codes if the NSBU switch is bad?
The TCM compares the NSBU switch reading with the internal pressure switch manifold. If they don't agree, PSM codes may set even though the PSM itself may be fine.

Will this fit my 2004.5 or newer truck?
No. For 2004.5-2005 and 2006-2019 trucks, see the switches listed in Before You Order.

For warranty information, see our Warranty Policy.

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