What does a modulator look like on a chevy 1500 2001 truck

The 1987 Chevy S10 2.5L typically only has one Engine Control Module (ECM), also known as the Powertrain Control Module (PCM). However, it is possible that some variations or modifications of the vehicle may have additional control modules for specific functions, such as the transmission control module (TCM), body control module (BCM), or anti-lock brake system module (ABS), but these are not considered part of the engine control system.

Partial wiring diagrams are usually available, but if you want a full wiring schematic, you need a workshop manual or a subscription to a website.

https://www.justanswer.com/chevy/2iqt1-color-code-ignition-module-1988-chev-s10.html

https://www.google.com/search?q=1987+Chevy+S10+2.8+spark+module+color+code+wiring+diagram

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Question edited for clarity.
Question moved to model category.

The OnStar module, called the VCIM, is under the dash, just above and to the left of the brake pedal

In the link

https://www.google.com/search?q=2022+Chevy+Silverado+LTD.+OnStar+module+location

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Transmission control module is part of the PCM - powertrain control module . Engine an transmission module all in one . It's in the engine compartment .
Powertrain Control Module (PCM) 4.8L,5.3L,6.0L
Near the left front inside the engine compartment

1999 CHEVROLET BLAZER Body Control Module (BCM)

www.rockauto.com/catalog/x,carcode,1353619,parttype,2888

... V6 > Electrical > Body Control Module (BCM). 1999 CHEVROLET BLAZER 4.3L V6 : Electrical : Body Control Module (BCM), Price, Core, Total, Add to Cart ...

electric problem maybe bcm? - Blazer Forum - Chevy Blazer Forums

blazerforum.com > ... > 2nd Gen S-series (1995-2005) Tech

Oct 25, 2009 - I have seen on line it could be the bcm module. ... In my 1999 Chevrolet Blazer it is located under the cd/radio and computer climate control. Looking for a Diagram or Info on the Body Control Module
Feb 4, 2012
body control module
Sep 25, 2009
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ACDelco 19153625 GM Original Equipment Body Control ...

if you mean modulator, it is usually held in place with a "U" style mounting bracket retained by one bolt at the side of the trans...will have vacuum hose attached...

Please verify the year of your truck. A 2003 Chevy Trailblazer has a 4L60E transmission. This transmission does not have a vacuum modulator valve. The 4L60 uses a vacuum modulator valve but the last year for that transmission was 1992. The perpose of the modulating valve is to control/regulate line pressure. The line pressure in a 4L60E is computer controlled or controlled electrically.

The Sensing diagnostic module is under the passenger seat under the carpet

Powertrain Control Module = under right side of dash, near blower motor.
Engine Control Module = same as above
Vehicle Control Module = same as above

All Suburban vehicles are equipped with only one of these choices. Good luck.