Spicer TPCS Troubleshooting Guide User Manual

Page 41

Service Codes

Group: 5P! (Codes 26, 27,

28
)

Low Pressure Reading (Codes 26, 27, 28)

Using the diagnostic tool, check faults to
identify the faulty channel:

Front (26)
Rear (27)
Trailer (28)

Initiate inflate mode for the faulty channel.

Yes

Replace PCU and recheck system.

Note: While replacing the PCU, pay particular

attention to possible air line contamination (e.g.,

oil, water, particles) which may suggest further

air system maintenance needs.

Refer to Service Manual

Replace ECU and recheck system.

Note: ECUs are not a typical cause of problems. If

an ECU is replaced, the system should be carefully

rechecked to make sure the problem has been

fixed and does not reoccur.

Is there extreme

pressure loss?

Identify cause of air loss,

repair and recheck system.

Refer to Service Manual

Use the diagnostic tool to pressurize

and hold the faulty channel.

Does pressure

drop quickly?

Locate leak (check axle

vents for air leakage also),

repair and recheck system.

Does the

pressure switch

open?

Replace pressure switch

and recheck system.

Refer to Service Manual

Does fault

reoccur?

Complete

Verify that the pressure switch opens

when the supply tank is below 80 psi.

Note: Primary and secondary air brake

gauges do not reflect actual pressure in

the supply tank.

Is there a

restricted line between

the wet tank and

PCU?

After a pressure

check, is the pressure

reading <5 psi?

Replace PCU sensor

and recheck system.

Check harness and PCU for open supply or

control solenoids. See Group 12C! PCU

Solenoids, Codes 54 or 56 for procedure.

Yes

Identify cause of air loss,

repair and recheck system.

Refer to Service Manual

Yes