Fault Code Guide

Fire Pump Controls Function Electrical Diagnosis
Test
No.
Test Procedure Test Result Action
5 In ServiceLink, open the "Chassis Module Battery Inputs"
Datalink Monitor template.
Is Battery Power Feed No. 3 at approximately battery
voltage?
Yes
The problem is in one or both of
the fire pump solenoid output
circuits.
Make sure the fire pump solenoids
are wired to the correct CHM
output pins per the ServiceLink
CHM Configuration screen.
Check both fire pump solenoid
output circuits from the CHM to the
solenoids, including the solenoid
coil ground circuit, for opens.
Check both solenoid output circuits
between the CHM and solenoids
for short to ground. This will cause
the CHM solenoid output to shut off
due to high current. The current
draw must not exceed 0.85A.
Check the solenoid(s). See
Section 42.19.
If all of the above is OK, replace
the CHM.
No
Check fuse 13 in the PDM. If
blown, locate and correct the
source of high current.
If fuse 13 is OK, check wiring
between PDM fuse 13 and CHM
pin C4-J for open circuit.
Table 2, Fire Pump Controls Function Electrical Diagnosis
PTO and Fire Pump Control Switch and Interlocks Test
Test
No.
Test Procedure Test Result Action
1 In ServiceLink, open the "Dash Smart Switches" Data Monitor
template.
NOTE: Be sure to open the correct template for the BHM
software version on the vehicle.
Look at each of the five BHM outputs: SS1 ID#, SS2 ID#,
SS3 ID#, SS4 ID#, and SS5 ID#.
If diagnosing the PTO, are any of the five SSn ID#s equal to
38?
If diagnosing the fire pump controls, are any of the five SSn
ID#s equal to 104?
Yes
Go to test no. 6.
No
Go to test no. 2.
PTO and Pump Electrical Controls 54.38
Troubleshooting
Business Class M2 Workshop Manual, Supplement 22, September 2012 300/5