heating CHEVROLET DYNASTY 1993 Service Manual

Fig. 1 Pin outs for 21-way Connector at ATC Computer Connector
Ä HEATING AND AIR CONDITIONING 24 - 75

Fig. 2 Pin outs for 14-way Connector at ATC Harness on A/C Housing
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(5) Check resistance across pins #4 and #5 of the
21-way connector for a shorted actuator motor. Resis-
tance should be between 20 and 50 ohms. If not cor-
rect, replace actuator.DIAGNOSTIC TROUBLE CODE 4ÐACTUATOR DRIVE COMMON SIGNAL NOT HIGH
If both Diagnostic Trouble Codes 4 and 5 oc-
cur simultaneously, do both procedures. There
is typically only 1 failure.
Fig. 3 Pin outs for 4-Way Connector
Fig. 4 Pin outs for Sun Sensor 2-Way Connector
Ä HEATING AND AIR CONDITIONING 24 - 77

(1) Disconnect terminal #4 on the ATC control 21-
way connector and retest the system. Removing this
terminal may generate additional Diagnostic Trouble
Codes. Disregard these at this time. (2) If Diagnostic Trouble Code 4 reappears, replace
control. (3) If code 4 does not reappear, the problem is a
shorted actuator motor or a short to ground in circuit
#34 (pin #4). (4) Remove 21-way connector and check for conti-
nuity from pin #4 to chassis ground. There should
not be any continuity. If continuity is there, repair
wiring and retest. (5) Check resistance across pins #4 and #5, #4
and #6, and #4 and #15 of the 21-way connector for
a shorted actuator motor. Resistance should be be-
tween 20 and 50 ohms. If not correct, replace actua-
tor involved.
DIAGNOSTIC TROUBLE CODE 5ÐFRESH/ RECIRC ACTUATOR DRIVE SIGNAL NOT HIGH
If both Diagnostic Trouble Codes 4 and 5 oc-
cur simultaneously, do both procedures. There
is typically only 1 failure. (1) Disconnect terminal #15 on the ATC control
21-way connector and retest the system. Removing
this terminal may generate additional Diagnostic
Trouble Codes. Disregard these at this time. (2) If Diagnostic Trouble Code 5 reappears, replace
control. (3) If code 5 does not reappear, the problem is a
shorted fresh/recirc door actuator motor. It could also
be a short to ground in circuit #32 (pin #15). (4) Remove 21-way connector and check for conti-
nuity from pin #15 to chassis ground. There should
not be any continuity. If continuity is there, repair
wiring and retest. (5) Check resistance across pins #15 and #4 of the
21-way connector for a shorted actuator motor. Resis-
tance should be between 20 and 50 ohms. If not cor-
rect, replace actuator.
DIAGNOSTIC TROUBLE CODE 6ÐCOMPRESSOR DRIVE SIGNAL NOT HIGH
(1) Disconnect the low pressure cut out switch and
retest diagnostics. (2) If code 6 does not reappear, then the problem is
in the A/C signal circuit C02. Check for wiring prob-
lem between the low pressure cut out switch and the
engine controller, or a bad engine controller. (3) If code 6 does reappear, remove the 21-way con-
nector from the control and check for a short between
pin #13 and chassis ground. This test will check the
wire from the control to the low pressure cut out
switch for a short to ground.
Fig. 5 Pin outs for 6-Way Connector In-Car Sensor and Sun Sensor
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Fig. 6 ATC Circuits
Ä HEATING AND AIR CONDITIONING 24 - 79

(4) If pin #13 shows continuity, repair circuit C02
and retest. (5) If no continuity is shown, replace the ATC con-
trol and retest.
DIAGNOSTIC TROUBLE CODE 7ÐBLOWER DRIVE SIGNAL NOT HIGH
First check the 4-way connector to the power
module for correct installation (1) With the ignition ON, check for ignition volt-
age to the power module pin #1 from the ATC con-
trol. If ignition is present at the power module,
proceed to step 3. If not proceed to step 2. (2) With the 21-way connector still connected and
the ignition ON, check for power module ignition
feed at the control pin #12. If ignition is not present,
replace the control. If ignition voltage is present, re-
pair the open in the wire between the control pin
#12 and power module pin #1. Retest system. (3) Turn ignition OFF and disconnect the 21-way
connector. Measure the resistance between pins #2
and #12. The resistance should read between 2,600
and 2,800 ohms. If correct, replace the ATC control.
If not correct, proceed to step 4. (4) Remove the 4-way connector from the power
module. Check for continuity between the ATC con-
trol pin #2 and power module pin #2. If no continu-
ity is shown, repair the wire for an open. If
continuity is shown, replace the power module and
retest.
DIAGNOSTIC TROUBLE CODE 8ÐA/D CONVERTOR INTERNAL FAILURE
Diagnostics will indicate a Diagnostic Trouble Code
8 if the internal reference voltage of the A/D Conver-
tor is not correct. This Diagnostic Trouble Code is
not serviceable. If a Diagnostic Trouble Code 8 oc-
curs, the computer control head must be replaced.
DIAGNOSTIC TROUBLE CODE 9ÐSUN LOAD SENSOR FAILURE
(1) Unplug the 21-way connector from the control
and check pin #19 for continuity to chassis ground.
If continuity is present, repair the wire shorted to
ground. If no continuity is present, proceed to step 2. (2) Plug the 21-way connector back in. Remove pin
#19 from the 21 way connector and run diagnostics
again. If Diagnostic Trouble Code 9 is still present,
replace the control. If code 9 is not present, replace
the sun sensor.
DIAGNOSTIC TROUBLE CODE 10ÐWATER TEMPERATURE SENSOR FAILURE
(1) Disconnect 21-way connector at control. Mea-
sure resistance between pin #17 and pin #7. This
value will change with temperature. Refer to Tem-
perature ReferenceÐDiagnostic Trouble Code 10
chart. (2) Check for continuity between pin #17 and
chassis ground. If continuity is present, repair and
retest.
DIAGNOSTIC TROUBLE CODE 11ÐAMBIENT TEMPERATURE SENSOR FAILURE
(1) Disconnect 21-way connector at control. With
an ohmmeter, measure the resistance between pin
#9 and pin #7. Refer to the Temperature Refer-
enceÐDiagnostic Trouble Code 11 chart.
(2) Check for continuity between pin #9 and chas-
sis ground. If continuity is present, repair and retest.
TEMPERATURE REFERENCEÐDIAGNOSTIC TROUBLE CODE 10
TEMPERATURE REFERENCEÐDIAGNOSTICTROUBLE CODE 11
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DIAGNOSTIC TROUBLE CODE 12ÐIN-CAR TEMPERATURE SENSOR/ASPIRATORFAILURE
(1) Disconnect 21-way connector at control. With
an ohmmeter, measure the resistance between pin
#20 and pin #7. Refer to Temperature Refer-
enceÐDiagnostic Trouble Code 11 chart for electrical
values. (2) Check for continuity between pin #20 and
chassis ground. If continuity is present, repair and
retest.
DIAGNOSTIC TROUBLE CODE 13ÐBLEND DOOR FAILED TO DRIVE TO HEAT POSITION
(1) Check door and linkage for binding.
(2) Disconnect 21-way connector from control head
and the 5-way connector from the blend air door ac-
tuator. Check continuity between pin #6 of the 21-
way connector and pin #5 of the 5-way connector. If
continuity is shown, go to step 3. If continuity is not
shown, repair circuit for an open circuit and retest
system. (3) Plug in the 5-way connector and check for re-
sistance between pins #4 and #6 of the 21-way con-
nector. A resistance of 20-50 ohms should be present.
If not, replace actuator. If correct, proceed to step 4. (4) If steps 1 and 2 indicate no failures, replace the
ATC control head.
DIAGNOSTIC TROUBLE CODE 14ÐBLEND DOOR FAILED TO DRIVE TO COLD POSITION
First check the 5-way connector to the blend
air door actuator for proper connection (1) Check door and linkage for binding.
(2) Remove the 21-way connector from the control.
With ignition ON, check for ignition voltage between
pin #8 of the 21-way connector and chassis ground.
If voltage is present, repair circuit for short to igni-
tion voltage. If voltage is not present, proceed to step
3. (3) Turn ignition OFF. With the 21-way still re-
moved, disconnect the 5-way connector from the
blend air door actuator. Check for continuity between
pin #8 of the 21-way connector and pin #1 of the
5-way connector. If continuity is not present, repair
open circuit. If present, continue to step 4. (4) Install the 5-way connector back into the blend
air door actuator and check for continuity between
the pins #7 and #8 of the 21-way connector. If con-
tinuity is present, replace the ATC control. If conti-
nuity is not present, replace the blend air door
actuator.
DIAGNOSTIC TROUBLE CODE 15ÐBLEND DOOR FEEDBACK SHORTED TO GROUND
(1) Remove the 21-way connector from the control
and the 5-way connector from the blend air door ac-
tuator. (2) Check for continuity between pin #8 of the 21-
way connector and chassis ground. If present, repair
circuit for short to ground. If not present, continue to
step 3. (3) Plug in the 5-way connector and measure resis-
tance between pins #7 and #8 of the 21-way connec-
tor. If the resistance is less than 10 ohms, replace the
actuator. If not, replace the control head.
DIAGNOSTIC TROUBLE CODE 16ÐMODE DOOR MOVED DURING BLEND DOOR TEST
(1) Remove the 21-way connector from the control
and the 5-way connector from the three actuators. (2) Check for continuity between pin #4 of the 21-
way connector and pin #4 of each actuator. If conti-
nuity is not present for a particular actuator circuit,
repair that circuit and retest system. If continuity is
present for all circuits, continue to step 3. (3) Plug in the 5-way connectors and check for re-
sistance between pins #4 and #6 of the 21-way con-
nector for the blend air actuator. Then check pins #4
and #5 of the 21-way for the mode actuator. The re-
sistance should be between 20-50 ohms. If either of
the actuators do not pass the resistance tests, replace
that particular actuator and retest the system. If
both pass the resistance test, replace the ATC con-
trol.
DIAGNOSTIC TROUBLE CODE 17ÐMODE DOOR FAILED TO DRIVE TO DEFROST
(1) Disconnect 21-way connector from control head
and the 5-way connector from the blend air door ac-
tuator. Check continuity between pin #5 of the 21-
way connector and pin #5 of the 5-way connector. If
continuity is present, proceed to step 2. If continuity
is not present, repair open circuit and retest system. (2) Plug in the 5-way connector and check for re-
sistance between pins #4 and #5 of the 21-way con-
nector. A resistance of 20-50 ohms should be present.
If not, replace actuator. If correct, proceed to step 3. (3) If steps 1 and 2 do not indicate any failures, re-
place the ATC control head.
DIAGNOSTIC TROUBLE CODE 18ÐMODE DOOR FAILED TO DRIVE TO PANEL
Check the 5-way connector to the mode door
actuator for proper installation. (1) Check the door and linkage for binding.
(2) Remove the 21-way connector from the control.
With ignition ON, check for ignition voltage between
pin #16 of the 21-way connector and chassis ground.
If voltage is present, repair circuit for short to igni-
tion voltage. If voltage is not present, proceed to step
3. (3) Turn ignition OFF. With the 21-way connector
still removed, disconnect the 5-way connector from
the mode door actuator. Check for continuity be-
tween pin #16 of the 21-way connector, and pin #1
Ä HEATING AND AIR CONDITIONING 24 - 81

of the 5-way connector. If continuity is not present,
repair circuit for an open. If present, continue to step
4.(4) Install 5-way connector back into the mode
door actuator. Then check for continuity between
pins #7 and #16 of the 21-way connector. If continu-
ity is present, replace the ATC control. If continuity
is not present, replace the mode door actuator.
DIAGNOSTIC TROUBLE CODE 19ÐMODE DOOR FEEDBACK SHORTED TO GROUND
(1) Remove the 21-way connector from the control,
and the 5 way connector from the mode door actua-
tor. (2) Check for continuity between pin #16 of the
21-way connector and chassis ground. If present, re-
pair circuit for short to ground. If not present, con-
tinue to step 3. (3) Plug in the 5-way connector and measure resis-
tance between pins #7 and #16 of the 21-way con-
nector. If the resistance is less than 10 ohms, replace
the actuator. If not, replace the control head.
DIAGNOSTIC TROUBLE CODE 20ÐBLEND DOOR MOVED DURING MODE DOOR TEST
(1) Remove the 21-way connector from the control
and the 5-way connector from the three actuators. (2) Check for continuity between pin #4 of the 21-
way connector and pin #4 of each actuator. If conti-
nuity is not present for a particular actuator circuit,
repair that circuit and retest system. If continuity is
present for all circuits, continue to step 3. (3) Plug in the 5-way connectors and check for re-
sistance between pins #4 and #6 of the 21-way con-
nector for the blend air actuator. Then check pins #4
and #5 of the 21-way connector for the mode actua-
tor. The resistance should be between 20-50 ohms. If
either of the actuators do not pass the resistance
tests, replace that particular actuator and retest the
system. If both pass the resistance test, replace the
ATC control.
DIAGNOSTIC TROUBLE CODE 21ÐROM CHECK SUM ERROR
During the Diagnostics test, the computer will ver-
ify it's own internal program. If it finds any part to
be bad, a Diagnostic Trouble Code 21 will be set.
This Diagnostic Trouble Code is not serviceable. If a
Fail Code 21 occurs, the ATC Control Module must
be replaced.
DIAGNOSTIC TROUBLE CODE 22ÐCOMPUTER ERROR
If incorrect data is found in the ATC Control com-
puter module, a Diagnostic Trouble Code 22 will be
set. This Fail Code is not serviceable. If a Diagnostic
Trouble Code 22 occurs, the ATC Control Module
must be replaced.
DIAGNOSTIC TROUBLE CODE 23ÐBLEND
DOOR FEEDBACK FAILED
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 23 will be stored within
the ATC Control, and must be cleared after the fail-
ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 from ATC Control. Follow service procedures for Diagnostic Trouble
Codes 14 and 15 when repairing.
DIAGNOSTIC TROUBLE CODE 24ÐMODE DOOR FEEDBACK FAILED
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 24 will be stored within
the ATC Control, and must be cleared after the fail-
ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 From ATC Control. Follow service procedures for Diagnostic Trouble
Codes 18 and 19 when repairing.
DIAGNOSTIC TROUBLE CODE 25ÐAMBIENT TEMPERATURE SENSOR FAILURE
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 25 will be stored within
the ATC Control, and must be cleared after the fail-
ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 from ATC Control. Follow service procedures for Diagnostic Trouble
Code 11 when repairing.
DIAGNOSTIC TROUBLE CODE 26ÐIN-CAR TEMPERATURE SENSOR/ASPIRATOR FAILED
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
24 - 82 HEATING AND AIR CONDITIONING Ä

back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 26 will be stored within
the ATC Control, and must be cleared after the fail-
ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 from ATC Control. Follow service procedures for Diagnostic Trouble
Code 12 when repairing.
DIAGNOSTIC TROUBLE CODE 27ÐSUN LOAD SENSOR FAILED
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 27 will be stored within
the ATC Control, and must be cleared after the fail-
ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 from ATC Control. Follow service procedures for Diagnostic Trouble
Code 12 when repairing.
DIAGNOSTIC TROUBLE CODE 28ÐWATER TEMPERATURE SENSOR FAILED
This Diagnostic Trouble Code is set during normal
ATC operation. The Diagnostic Trouble Code will be
set only after the ATC control has been operating for
15 minutes. The control will compensate for the feed-
back failure immediately upon power up, but the Di-
agnostic Trouble Code will not be set until the time
limit has been met. Diagnostic Trouble Code 28 will be stored within
the ATC Control and must be cleared after the fail- ure has been repaired. To clear this Diagnostic Trou-
ble Code, refer to Erasing Diagnostic Trouble Codes
23 through 28 from ATC Control. Follow service procedures for Diagnostic Trouble
Code 10 when repairing.
ERASING DIAGNOSTIC TROUBLE CODES
Diagnostic Trouble Codes 23 through 28 are stored
within the ATC in the computer memory. These
codes may be erased from the memory after the cor-
rect repairs have been made. Intermittent Diagnostic
Trouble Codes 23 through 28 will be stored until
they are erased. (1) Run the DIAGNOSTIC TEST.
(2) Depress the PANEL button to access all Diag-
nostic Trouble Codes. When the Display begins flash-
ing alternating zeros, you can do three things:
² Do nothing, and in five seconds control will return
to normal ATC operation. All codes will remain
stored in the control.
² Depress any button within five seconds, other than
A/C, and stop the test immediately. Control will re-
turn to normal ATC operation.
² Depress the A/C button within five seconds, and
proceed to the erasing procedure. By depressing the
A/C button, you will not erase any Diagnostic Trou-
ble Codes. You will only access the next part of the
procedure. Proceed to step 3. (3) After you depress the A/C button the display
will alternate E's. This is for ERASE. You can now
do two things:
² Do nothing, and in five seconds, all Diagnostic
Trouble Codes from 23 through 28 will be erased
from the ATC control.
² Depress any button within five seconds, and Diag-
nostic Trouble Codes will not be erased. Control will return to normal ATC operation.
Ä HEATING AND AIR CONDITIONING 24 - 83

The oxygen sensor contains a heating element that
keeps it at proper temperature during all operating
modes. Maintaining correct sensor temperature at all times allows the system to enter into closed loop op-
eration sooner and remain in closed loop during pe-
riods of extended idle.
In Closed Loop operation the powertrain control
module (PCM) monitors the O
2sensor input (along
with other inputs) and adjusts the injector pulse
width accordingly. During Open Loop operation the
PCM ignores the O
2sensor input. The PCM adjusts
injector pulse width based on preprogrammed (fixed)
oxygen sensor input values and the current inputs
from other sensors.
REMOVAL
CAUTION: Do not pull on the oxygen sensor wire
when disconnecting the electrical connector.
WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
Fig. 6 Heated Oxygen SensorÐ2.5L Engine
Fig. 7 Heated Oxygen SensorÐ2.5L MPI Engine (Flexible Fuel AA-body)
Fig. 8 Heated Oxygen SensorÐTurbo III Engine
Fig. 9 Heated Oxygen SensorÐ3.0L Engine
Fig. 10 Heated Oxygen SensorÐ3.3L/3.8L Engine
Ä EMISSION CONTROL SYSTEMS 25 - 19