The scan tool indicates Diagnostic Trouble Code (DTC) P0138: A high voltage problem in the Secondary Heated
Oxygen Sensor (HO2S) (Sensor 2) circuit.
— The MIL has been reported on.
— DTC P0138 is stored.
Problem verification:
1. Do the PCM Reset Procedure.
2. Start the engine. Hold the
engine at 3,000 rpm with no
load (in Park or neutral) until
the radiator fan comes on.
3. Check the secondary HO2S
(Sensor 2) output at 3,000 rpm
voltage with the scan tool.
Does the voltage stay at 0.6 V
or more?
YES
Check for an open in the HO2S:
1. Turn the ignition switch OFF.
2. Disconnect the secondary
HO2S (Sensor 2) connector.
3. Install a jumper wire between
the secondary HO2S (Sensor 2)
connector (harness side) No. 1
terminal and No. 2 terminal.
4. Turn the ignition switch ON (II).
5. Check the secondary HO2S
(Sensor 2) output voltage with
the scan tool.
Is there 0.6 V or more?
YES
Check for an open in the wire
(SO2S line):
1. Turn the ignition switch OFF.
2. Install a jumper wire between
the PCM connector terminals
F2 and F6.
3. Turn the ignition switch ON (II).
4. Check the secondary HO2S
(Sensor 2) output voltage with
the scan tool.
Is there 0.6 V or more?
YES
Substitute a known-good PCM
and recheck (see page
11-42
for
immobilizer information). If symp-
tom/indication goes away, replace
the original PCM.
NO
Intermittent failure, system is OK
at this time. Check for poor con-
nections or loose wires at C444
(located behind right kick panel),
C610 (secondary HO2S (Sensor
2)) and PCM.
SECONDARY HO2S (Sensor 2) CONNECTOR (C610)
SHO2S
(WHT/
RED)
SO2S GND
(GRN/WHT)
Wire side of female terminals
Replace the secondary HO2S (Sen-
sor 2).
JUMPER
WIRE
SO2S GND
(GRN/WHT)
Repair open in the wire between
PCM (F2) or (F6) and secondary
HO2S (Sensor 2).
Wire side of female terminals
NO
PCM CONNECTOR F (8P)
SO2S
(WHT/RED)
JUMPER WIRE
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