Bulletin No.: PIT6198
Published date: 07/11/2024

Preliminary Information
PIT6198 Diagnostic Tip - SES MIL On At Startup With DTC U0100
Models
Brand:

Model:

Chevrolet Silverado 1500
Chevrolet Silverado 1500
Chevrolet

Silverado 1500 New (RPO J21,
VIN Digit 5 = W or Y)

Chevrolet Silverado 2500/3500 HD
GMC

Sierra 1500 (New Model)

GMC

Sierra 1500

GMC
GMC

Model
Years:

2019 (New
All
Model)
2020 All
2021
2022
2020 2022
2019
2020 2021

Sierra 1500 New (RPO J21, VIN
2022
Digit 5 = 8 or 9)
2020 Sierra 2500/3500 HD
2022

Involved Region or
Country

Condition

VIN:
Engine: Transmissions:
from to
All All

All

All All

All

All

All All

All

All

All All

All

All

All All

All

All

All All

All

All

All All

All

All

All All

All

North America

Some customers may comment on a SES MIL at startup. When
checking for DTC's modules will have set a U0100 for loss of
communication with the ECM. In some cases, there may or may
not be the following issues:
- DTCs P0700 and/or U18D5
- Transmission shifting issues

Cause

The cause of this concern could be the ECM missing the
accessory wake up input on circuit 5985, see example SI
document 4938084.

Correction:
Using a voltmeter check for power on circuit 5985 at the ECM. There should be
approximately 12 volts present with the BCM awake. You may notice with the ignition
turned off, there is still voltage present. This is because the BCM may still be awake. This
should be considered normal. If no or low voltage is found, use the appropriate wiring
diagram for the vehicle you are working on and perform normal circuit diagnosis.

Tip: Circuit 5985 is a low amperage signal circuit and it may not be able to power certain
test lights or bulbs. The use of a voltmeter and small bulb, example 194 bulb, is required
to test the circuit. With a battery charger/maintainer connected, attach one side of a 194
bulb to circuit 5985 and the other side to a good ground (battery negative). Next, wake up
the BCM (by turning the headlights on, turning the ignition on, ect.) and make sure the
bulb lights. If the bulb does NOT light, inspect for high resistance/open/shorts in circuit
5985. If the bulb lights, use a voltmeter and measure the voltage across the 194 bulb, to
make sure there is at least 11 volts, if not inspect for high resistance/open/shorts in circuit
5985.
NOTE: A 194 bulb draws approximately 250 ma. Attaching too much of a load to circuit
5985 will pull the voltage down below 11 volts and lead to misdiagnosis.
Known areas for high resistance/open/shorts in circuit 5985 are:
- Broken/corroded/damage circuit within the first 12 inches from the ECM connectors.
- Areas listed in bulletin 21-NA-149

Warranty Information
For wiring repairs covered under warranty, please refer to latest version of bulletin 10-0089-005 for warranty information on wire/connector repairs.

Version History
Version

1

Modified

07/11/2024 - Created on.

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