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Title : S13 Brake Switch Diagnostics
Applies To : LT, RH, HV, HX with S13 engine

CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
12/09/2025 - Changed step 8 and 9 as steps were not clear. Corrected pin numbers.
04/23/2025 - corrected redundant and brake switch 1 part numbers
04/22/2025 - Initial Article Release

DESCRIPTION
This document is intended to provide supplemental information for concerns with brake light switches and pressure sensors used by the BCM and PIM
module to determine if the operator of the vehicle is applying the service brakes. All S13 vehicles are equipped with BCM feature 597483 (BCM PROG,
BRAKE SWITCH, Use With Brake Application Pressure Switch). 597483 uses a normally open brake pressure switch that closes with 2-6 psi of air pressure
and a brake application pressure sensor. When the switch is closed or the pressure sensor reads higher than 4psi, the BCM considers the brakes applied
and will broadcast that over the J1939 networks to other modules. The S13 also includes a redundant brake switch that is wired directly to the PIM. This
switch is normally closed and opens with 2-6 psi of air pressure. If the S13 ECM believes the brakes are applied from one of these brake signals, it can
reduce or completely cut throttle input.
NOTE: All Next Gen 2024MY+ CE buses also use this feature; it is optional on other vehicles as well. These diagnostics can also be used on those vehicles,
but the symptoms will be different.

SYMPTOM(s)
Diagnostic Trouble Code(s) & Dashboard Indicator Light(s):

DTC/Light

Description

SA 33 SPN 116 FMI 15

Brake Switch and Pressure
Transducer are Mismatched High

SA 33 SPN 116 FMI 17
SA 33 SPN 597 FMI 0
SA 33 SPN 597 FMI 1

SA 0 SPN 603 FMI 17

Customer Observations or Concerns:
Low engine power
No Response from the Throttle pedal

Notes

If the pressure sensor reads more than 15 psi for 30 seconds while
the brake switch input is inactive, this fault is set. This fault will cause
brake lights to illuminate when active. Remember that a pressure
reading above 4psi means the BCM considers the brakes applied so
this fault may not necessarily set when the symptoms are present.
If the pressure sensor reads less than 1 psi for 30 seconds while the
Brake Switch and Pressure
brake switch input is active, this fault is set. This fault will cause brake
Transducer are Mismatched Low
lights to illuminate when active.
Brake Switch reading above normal Brake Switch (Connector J5/1602 pin E14) Shorted High or Open
range.
Circuit
Brake Switch reading below normal
Brake Switch (Connector J5/1602 pin E14) Short To Ground
range
Fault means the ECM sees the brake signal from the BCM showing
Brake Pedal Switch 2 : Data Valid
applied while the redundant brake switch shows released. This fault
But Below Normal Operating Range
does not mean there is a problem with the redundant brake switch or
– Least Severe Level
it's circuits.

Brake lights stuck on

SPECIAL TOOLS / SOFTWARE
Tool Description

Tool Number

Diamond Logic® Builder

Comments

Instructions

EZ-Tech Software

SERVICE PARTS INFORMATION
Quantity
Notes
Required
Brake Application Pressure Sensor. The same part is
1
used for primary and secondary tank pressure sensors
and ESP brake pressure sensors.

Kit Description

Part Number

Switch, Sensor, Transducer Pressure

4192764C1

Switch, Stop/brake Light

2505850C2

1

Brake Switch 1 is wired to the BCM

Switch, Sensor, Pressure Switch

4200246C1

1

Redundant brake switch wired to PIM module

TERMINAL CABLE*DELPHI MICRO-PA

3539904C1

1

Terminal pin E3 1602 connector at BCM

DIAGNOSTIC STEP(s)
Note: These diagnostics are written for level 2 (or higher) dealer or fleet access in DLB.

Step Action

Decision

If there are network communication codes on the 500K powertrain network,
Yes - Brake Switch Signal is showing
performance-related fault codes stored in the ECM/PIM, and/or brake switch-related as depressed when service brakes are
faults, follow the FCAPS for these faults and address them before proceeding with
not applied. Go to Step 2.
this diagnostics.
If there is a complaint of low power, throttle cut, no response from the accelerator
pedal, with no fault codes, then check the brake switch signal in SDS when
connected to the engine.

1

Does the brake switch signal show the brakes are depressed when the concern
happens?

No - Brake switch is not showing as
depressed when concern
occurs. Consult applicable engine lowperformance diagnostics.

Step Action
2

1. Connect to the vehicle with Diamond Logic Builder (DLB) Software and enter diagnostics mode.
2. Go to the features tab, select feature 597483, and click the "Make Session" button.

Decis
No - B
Servic
is grea
Brake_
unche
pressu
high: G

No - B
Servic
is less
Brake_

checke
shorte

Yes. D
unche
applied
to PIM
SDS th
are app
When c

Figure 1: 597483 Session in DLB
Item 1: Record/Arm Button

Step Action

3

Decision

3. With
vehicle
to drive,
startreading
recording
by 4hitting
the no
record/arm
F2 keys
(Figure or
1, voltage
Item 1). is
With
thethe
issue
stillready
present
(sensor
over
psi with
brake button or Alt
Noand
- high
resistance
application), unplug the brake application pressure sensor and check the
higher than .5V. The ZVR circuit has
4. While trying
topin
replicate
thesensor
complaint,
the signals
Service_Brake_App_Air_Sensor_Signal
and
resistance
from
2 at the
andwatch
ground.
It is also
recommended to
poor continuity
to Brake_Switch_Digital_Input.
ground. Inspect the
backprobe pin E3 in connector 1602 and check the voltage between that
circuit for the cause of high resistance.
Note: To
save
a recording
attach to a case file or for review later, go to the tools menu,
select
"Savethe
Graph
Data",
save the CSV file
circuit
and
a known
good to
ground:
Carefully
inspect
pin drag
of and
terminal
with an applicable name. Saving the session only saves the signals and not the data.E3 in the 1602 connector and pins A4 on
Resistance should be extremely low. Less than 5 ohms at most, ideally less than 1 both sides of the D490 connector (IP to
ohm, but meters can vary. Voltage should be less than .5V. Is resistance to the
DCM connection located by the steering
Is
Service_Brake_App_Air_Sensor_Signal
less than 4 psi and Brake_Switch_Digital_Input
unchecked
the brake
pedal is NOT
ground
reasonable?
column).
Inspectanytime
for damaged
or poorly
depressed?
done crimping of terminals to wire. Repair
the circuit as necessary. Replace the
terminal if necessary. Save the failed
terminal for warranty review.
Note: The most common cause of this
complaint has been the terminal in the E3
cavity of the 1602 connector.

Yes - resistance is good. Go to step 4.

Step Action
With the sensor disconnected, check for voltage between pin 1 and a known
good ground:
Is the voltage less than .5V?

No - the voltage is higher than .5V. The
sensor signal circuit has a short to
power. Carefully inspect the circuit
between the sensor connector and BCM
for shorts to other power circuits.

Yes - no issue with circuits. Replace the
brake application pressure sensor. If the
brake application pressure reading still
does not read properly, verify no air is
being trapped in the air circuits and use a
test BCM to verify the BCM has not failed.

4

Step Action
5

Decision

Decision

With the issue still present (Brake_Switch_Digital_Input is checked with no
No - high resistance or voltage is
brake application), unplug brake pressure switch 1 and check resistance from higher than .5V. The ZVR circuit has

pin D at the switch and a known good ground. It is also recommended to
backprobe pin E3 in connector 1602 and check the voltage between that
circuit and a known good ground:
Resistance should be extremely low. Less than 5 ohms at most, ideally less than 1
ohm, but meters can vary. Voltage should be less than .5V. Is resistance to the
ground reasonable?

poor continuity to ground. Inspect the
circuit for the cause of high resistance.
Carefully inspect the pin drag of the
terminal in the 1602 connector and pin B9
on both sides of the D490 connector (IP to
DCM connection located by the steering
column). Inspect for damaged or poorly
done crimping of terminals to wire. Repair
the circuit as necessary. Replace the
terminal if necessary. Save the failed
terminal for warranty review.

Yes - resistance is good. Go to step 6.

Step Action
With brake pressure switch 1 and BCM connector 1602 unplugged, check
resistance between pin C at the switch and pin E14 in the 1602 connector:
Resistance should be extremely low. Less than 5 ohms at most, ideally less than 1
ohm, but meters can vary. Is resistance reasonable?

6

Decision
No - high resistance on the
circuit. Inspect the circuit for the cause of
high resistance. Carefully inspect the pin
drag of terminal E14 in 1602 connector
and pin B9 on both sides of the D490
connector (IP to DCM connection located
by the steering column). Inspect for
damaged or poorly done crimping of
terminals to wire. Repair the circuit as
necessary. Replace the terminal if
necessary. Save the failed terminal for
warranty review.

Yes - resistance is good. Go to step 7

Step Action
With brake pressure switch 1 and BCM connector 1602 unplugged, check
resistance between pin C at the switch and a known good ground:

Decision
No - low resistance to ground on the
circuit. Inspect the circuit for damage and
shorts.

There should be little to no continuity between this circuit and ground (greater than
10000 ohms). Is there little to no continuity (high resistance) on this circuit?
Yes - no issue with circuits. Replace
brake pressure switch 1. If
Brake_Switch_Digital_Input is still
checked with no brake application, verify
no air is being trapped in the air circuits,
and use a test BCM to verify the BCM has
not failed.

7

Step Action
8

With the issue still present (SDS reporting brakes are applied with no brake
application), unplug the redundant brake pressure switch (connector D1812)
and check the resistance from pin D at the switch and a known good ground:
Resistance should be extremely low. Less than 5 ohms at most, ideally less than 1

Decision
No - high resistance. The ZVR circuit
has poor continuity to ground. Go to
step 9.

ohm, but meters can vary. Is resistance to the ground reasonable?

Yes - resistance is good. Go to step 10.

Step Action

9

Decision

With the redundant brake switch and PIM connector D1530 unplugged, check No - high resistance on the
the resistance between pin D at the switch and pin 30 in the D1530 connector: circuit. Inspect the circuit for the cause of
high resistance. Carefully inspect the pin
Resistance should be extremely low. Less than 5 ohms at most, ideally less than 1 drag of terminal 30 in D1530 connector at
ohm, but meters can vary. Is resistance reasonable?
the PIM. Also, inspect pin D3 on both
sides of the D490 connector (IP to DCM
connection located by the steering
column). Inspect for damaged or poorly
done crimping of the terminal to the wire.
Repair the circuit as necessary. Replace
the terminal if necessary. Save the failed
terminal for warranty review.

Yes - resistance is good. Go to step 10

Step Action
With the redundant brake switch and PIM connector D1530 unplugged, check
resistance between pin C at the switch and a known good ground:

Decision
No - low resistance to ground on the
circuit. Inspect the circuit for damage and
shorts.

There should be little to no continuity between this circuit and ground (greater than
10000 ohms). Is there little to no continuity (high resistance) on this circuit?

10

WARRANTY INFORMATION
Warranty Claim Coding:
Refer to the Warranty Coding Manual for Group and Noun Codes.

Standard Repair Time(s):
Refer to the SRT Manual for Repair Times

Yes - no issue with circuits. Replace
Redundant Brake Switch. If SDS still
shows brakes applied (and BCM doesn't)
with no brake application, verify no air is
being trapped in air circuits and use a test
PIM to verify the PIM has not failed.

OTHER RESOURCES
Master Service Information Site

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