186CNV / 284ANV: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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Code 52-02 OCT Shorted
The outdoor coil thermistor is used to determine when the outdoor coil is
completely cleared during defrost. For this reason all defrosts performed
when this fault is active will occur for the maximum time length allowed
by software. The sensor is monitored continuously and if resistance is
below 1kohm for 1 second this fault will occur. Once sensor value
increases above 1kohm for 1 second the fault will clear. This fault does
not escalate to a malfunction.
Measure resistance value of thermistor at the PCM connector. If value is
below 1kohm, look for a short in the wiring or at the connector itself. If
no shorts are observed, replace sensor. If measured resistance is within
allowable range, replace PCM.
*Note if any combination of OAT and OCT shorted/open are present the
system will limit operation based on each individual fault.
Code 53-41 OST Open - Backup Heat Only
The suction thermistor is required for control of the outdoor EXV in HP
systems. For this reason, heating mode operation will be locked out if the
OST is determined to be open or shorted. Cooling operation will be
allowed if OST is not functional, though on HP systems the malfunction
will be displayed on wall control screen. This will remind homeowner to
repair the sensor before heating season. Open OST sensor value will
default to "47" on status or checkout display. The sensor is monitored
continuously and if resistance is above 465kohm for 1 second this fault
will occur. Once sensor value drops below 465kohm for 1 second the
fault will clear.
Measure resistance value of thermistor at the PCM connector. If value is
above 465kohm, look for a break in the wiring or at the connector itself.
If no breaks are observed, replace sensor. If measured resistance is
within allowable range, replace PCM.
Code 53-42 OST Shorted - Backup Heat Only
The suction thermistor is required for control of the outdoor EXV in HP
systems. Similar to "OST Open" fault, heating mode operation will be
locked out if the OST is determined to be open or shorted. Cooling
operation will be allowed if OST is not functional, though on HP
systems the malfunction will be displayed on wall control screen. This
will remind homeowner to repair the sensor before heating season.
Shorted OST sensor value will default to "47" on status or checkout
display. The sensor is monitored continuously and if resistance is below
1kohm for 1 second this fault will occur. Once sensor value rises above
1kohm for 1 second the fault will clear.
Measure resistance value of thermistor at the PCM connector. If value is
below 1kohm, look for bare wire, short in the wiring, or at the connector
itself. If no bare wires or shorts are observed, replace sensor. If measured
resistance is within allowable range, replace PCM.
Code 54-01 ODT Open
The discharge thermistor is used to protect the compressor and ensure
discharge superheat is present at all times. When "ODT Open"
malfunction is active 47 will be substituted by default. The sensor is
monitored continuously and if resistance is above 310kohm for 1 second
this malfunction will occur. Once sensor value drops below 310kohm for
1 second the malfunction will clear. Since achieving discharge superheat
is an integral requirement for startup, when this sensor does not read a
valid value, the system will only run at startup speed. Normal operation
will resume once valid ODT value is read by PCM.
Measure resistance value of thermistor at the PCM connector. If value is
above 310kohm, and OAT and OCT measure above 25F, look for a break
in the wiring or at the connector itself. If no breaks are observed, replace
sensor. If measured resistance is within allowable range, replace PCM.
Code 54-02 ODT Shorted
The discharge thermistor is used to protect the compressor and ensure
discharge superheat is present at all times. When "ODT Shorted"
malfunction is active 47 will be substituted by default. The sensor is
monitored continuously and if resistance is below 670 ohm for 1 second
this malfunction will occur. Once sensor value rises above 670 ohm for 1
second the malfunction will clear. Since achieving discharge superheat is
an integral requirement for startup, when this sensor does not read a
valid value, the system will only run at startup speed. Normal operation
will resume once valid ODT value is read by PCM.
Measure resistance value of thermistor at the PCM connector. If value is
below 670 ohm, look for a short in the wiring or at the connector itself. If
no shorts are observed, replace sensor. If measured resistance is within
allowable range, replace PCM.
Code 57-01 P1 Open Fault
Code 57-41 P1 Open Lockout
Code 58-01 P2 Open Fault
Code 58-41 P2 Open Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. This feature allows the pressure
transducers and harnesses to be interchangeable. Each pressure
transducer requires 3 wires: Ground (BLK), Power (+5V DC, RED), and
Signal (GRN). The ratio of voltage between power and signal wires is
converted into a pressure value. If the signal is above or below the
pressure transducers ability to measure it may be because the power wire
is not supplying 5V DC or the signal wire is not returning a DC Voltage
between 0.5-4.5 VDC. A base code of 57 or 58 is determined based on
which PCM connection has the issue, P1 or P2. The expansion codes 01
and 41 explain the type of issue, in this case "open", meaning the signal
wire is returning more than 4.5V DC. The most likely cause of this the
sensor wire being disconnected and the PCM board "pulling" up the
signal voltage to +5V DC.
Code 57-02 P1 Shorted Fault
Code 57-42 P1 Shorted Lockout
Code 58-02 P2 Shorted Fault
Code 58-42 P2 Shorted Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. This feature allows the pressure
transducers and harnesses to be interchangeable. Each pressure
transducer requires 3 wires: Ground (BLK), Power (+5V DC, RED), and
Signal (GRN). The ratio of voltage between power and signal wires is
converted into a pressure value. If the signal is above or below the
pressure transducers ability to measure it may be because the power wire
is not supplying 5V DC or the signal wire is not returning a DC Voltage
between 0.5-4.5 VDC. A base code of 57 or 58 is determined based on
which PCM connection has the issue, P1 or P2. The expansion codes 02
and 42 explain the type of issue, in this case "shorted", meaning the
signal wire is returning less than 0.5V DC. The most likely cause of this
the sensor wire being shorted to the metal chassis.
Code 57-43 P1 Sensor Lockout
Code 58-43 P2 Sensor Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. For this reason the pressure transducers
and harnesses are interchangeable. Each pressure transducer requires 3
wires: Ground (BLK), Power (+5V DC, RED), and Signal (GRN). The
ratio of voltage between power and signal wires is converted into a
pressure value. The pressure transducer is capable of sending a value to
PCM via sensor wire if it is not working correctly. A base code of 57 or
58 is determined based on which PCM connection has the issue, P1 or
P2. When a DC V value of 4.84-4.95 is returned to PCM it will trigger
57-43 or 58-43 fault. The most likely cause of this is a failed transducer
part. Switch the harnesses from P1 and P2 to see if the malfunction
follows the transducer. If so, follow procedure to replace failed pressure
transducer. Trace wires from PCM board connection to ensure correct
transducer is being replaced.
