Hummer H1 Service Manual page 303

5-104 Transmission/Transfer Case
DTC P1810 Pressure Switch Assembly
(PSA) Fault
Circuit Description
The PSA consists of five normally open pressure switches. The
PCM supplies battery voltage to each range signal. By ground-
ing one or more of these circuits through various combinations
of the switches, the PCM detects what manual valve position
has been selected. It then compares actual voltage combina-
tions to a PSA chart in PCM memory.
The PSA switch assembly cannot distinguish between Park and
Neutral because the monitored valve body pressures are identi-
cal in both cases. With the ignition "on" and engine "off,"
Park/Neutral will be indicated. When the transmission 20-way
connector is disconnected, ground potential for the three range
signals is removed, and with ignition "on," D2 will be indi-
cated.
This DTC detects an invalid state of the PSA sensor or the PSA
circuit by deciphering the PSA inputs.
Conditions For Setting DTC
This DTC will set if any of the following conditions occurs:
Condition 1:
• No system voltage DTC P0560.
• Engine running.
• PCM detects an illegal PSA combination for greater
than 25 seconds.
Automatic
Transmission
Fluid
Pressure
Manual Valve
D2
Position
Switch
Switch
(TFP)
Switch
D4 D3
Switch Switch
D E
R
P
C34
C32-S C32-H
C29-B4 C29-B5
Trans
Trans
Range C Range B
Input Input
___________________________________________
Auto Trans Input Shaft
Speed Sensor
Lo
Rev
Switch
C
N
C32-K
Tw i s t e d
P a i r
C29-B6
Trans
Range A
Input
Condition 2:
• No system voltage DTC P0560.
• No DTCs P0722 or P0723.
• Engine speed is less than 50 rpm for.5 seconds, between
50 and 525 rpm for greater than 0.1 seconds, and than to
greater than 525 rpm and vehicle speed is less than 3
km/h (2 mph).
• PCM detects gear range as D2 before and after start-up.
• Condition exists for greater than 7 seconds and is
checked only at start-up.
A/T ISS
A
B
C32-A B
C27-D1
C27-D11
A / T ISS A / T ISS
Low
High
POWERTRAIN
CONTROL
MODULE
(PCM)
9-S12-071
®