Pontiac Fiero 1988 Service Manual page 481

8E2-A-26 DRIVEABILITY AND
EMISSIONS- FUEL INJECTION (TBS)
412
PPL
4-30-87
413
TAN
'OXYGEN(0
2
)SENSOR
ENGINE
GROUND
EXHAUST
B2
B23
ECM
0
2
SENSOR
SIGNAL
1 0
2
SENSOR
GROUND
05-18-87
: 7S 3204-6E
CODE 13
OXYGEN SENSOR CIRCUIT
(OPEN CIRCUIT)
2.5L "P" SERIES (TBI)
Circuit Description:
The ECM supplies a voltage of about of .45 volt between terminals "B2" and "B23". (If measured with 10
megohm digital voltmeter, this may read as low as .32 volts).
The O2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down through about
,10 volt, if exhaust is lean.
The sensor is like an open circuit and produces no voltage, when it is below 360° C
(600°F).
An open sensor
circuit, or cold sensor, causes "Open Loop" operation.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Code 13 will set:
• Engine at normal operating temperature.
•
At least 2 minutes engine time after start.
• O2 signal voltage steady between .35 and .55
volts.
• Throttle angle above 7%.
• All conditions must be met for about 60
seconds.
If the conditions for a Code 13 exist, the system
will not go "Closed Loop".
2. This test determines if the O2 sensor is the
problem, or if the ECM and wiring are at fault.
3. In doing this test, use only a high impedence
digital volt ohm meter. This test checks the
continuity of CKT(s) 412 and 413. If CKT 413 is
open, the ECM voltage on CKT 412 will be over .6
volts (600 mv).
Diagnostic Aids:
Normal "Scan" voltage varies between 100 mv to
999 mv (.1 and 1.0 volt), while in "Closed Loop". Code
13 sets in one minute, if voltage remains between .35
and .55 volts, but the system will go "Open Loop" in
about 15 seconds.
Verify a clean, tight ground connection for CKT
413. Open CKT(s) 412 or 413 will result in a Code 13.
If Code 13 is intermittent, refer to Section "B".