H30 DTCS P0135, P0141, P0155 AND P0161: HO2S HEATERSIGNAL CIRCUIT IS
OPEN, SHORTED TO GROUND, SHORTED TO B+ OR EXCESSIVECURRENT DRAW
Diagnostic Trouble Codes (DTCs) P0135, P0141, P0155and P0161 indicate a short to ground, open,
or short to VPWR in the HO2S heater circuit.
DTC/HO2S Reference List:
DTC P0135 = HO2S HTR-11
DTC P0141 = HO2S HTR-12
DTC P0155 = HO2S HTR-21
DTC P0161 = HO2S HTR-22
Possible causes:

Shorts to B+ in harness or HO2S.

Water in connectors.

Cut or pulled wires.

Disconnected wiring.

Open VPWR circuit.

Open GND circuit.

Low battery voltage.

Corrosion or poor mating terminals.

Damaged PCM.
 Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and proper assembly.
Note: On some applications, a vehicle hoist may be required to access the HO2S harness.
Were any concerns found during the visual inspection?
H31 PERFORM KEY ON ENGINE OFF (KOEO) SELF-TEST
 Key off.
 Scan Tool connected.
 Key on.
 Engine at 2000 rpm for 5 minutes.
 Key off.
 Key on, engine off.
 Activate KOEO Self-Test.
Are DTCs P0135, P0141, P0155 and/or P0161 present?
Yes No
REPAIR any concerns found in the visual
inspection. RERUN Quick Test .
GO to H31 .
Yes No
No DTCs present. FAULT may be intermittent.
H32 CHECK FOR VPWR AT THE VEHICLE HARNESS CONNECTOR
Note: If DTCs P0135 and P0155 or P0141 and P0161 are displayed, both heater circuits will require
testing. DTCs displayed separately are tested individually.
 Key off.
 Disconnect the appropriate HO2S(s).
 Inspect both ends of the connectors for damaged or pushed out pins, moisture, corrosion,
contamination, etc. Service as necessary.
 Key on, engine off.
 Measure the voltage between VPWR and SIG RTN circuit at the HO2S vehicle harness connector(s)
(refer to Schematic at the beginning of this Pinpoint Test).
Is the voltage greater than 10.5 volts?
H33 CHECK FOR OPEN VPWR CIRCUIT
 Key off.
 Install breakout box, PCM disconnected.
 Suspect sensor disconnected.
 Measure the resistance between the VPWR Test Pin atthe breakout box and VPWR at the HO2S
vehicle harness connector.
Is the resistance less than 4.0 ohms?
H34 CHECK HO2S HEATER RESISTANCE
 Key off.
 HO2S disconnected.
 Connect DVOM to HO2S HTR GND and VPWR Test Pins at the HO2S sensor connector, and
measure the resistance.
Is the resistance between 3 and 30 ohms?
GO to H32 .
GO to Pinpoint Test Step Z1 with the following
data: HO2S PIDs and a list of possible causes.
Yes No
GO to H34 . GO to H33 .
Yes No
GO to H34 .
CHECK fuse in circuit. If fuse is OK, REPAIR
open circuit. REMOVE breakout box.
RECONNECT all components. RERUN Quick
Test .
H35 CHECK FOR HEATER GND AND VPWR SHORTED TO HO2S CASE
 Suspect sensor disconnected.
 Measure the resistance between the HO2S Heater GND at the HO2S connector and the HO2S case.
 Measure the resistance between the HO2S Heater GND connector and the Signal RTN Pin.
 Measure the resistance between the HO2S VPWR at theHO2S sensor connector and the HO2S
sensor case.
Is the resistance greater than 10,000 ohms?
H36 CHECK FOR SHORTS TO OTHER GROUNDS AND VPWR IN THE HO2S
HEATER GROUND HARNESS CIRCUITS
 Key off.
 Disconnect Scan Tool from DLC.
 Suspect sensor disconnected.
 Disconnect PCM.
 Breakout box installed, leave PCM disconnected.
 Use the following list to measure the resistance between the appropriate test pins at the breakout
box.

DTC P0135 = HO2S HTR-11 (HTR GND)

Test Pin 93 and Test Pins 24, 76, 103, 91 and 97.

DTC P0141 = HO2S HTR-12 (HTR GND)

Test Pin 95 and Test Pins 24, 76, 103, 91 and 97.

DTC P0155 = HO2S HTR-21 (HTR GND)

Test Pin 94 and Test Pins 24, 76, 103, 91 and 97.

DTC P0161 = HO2S HTR-22 (HTR GND)

Test Pin 96 and Test Pins 24, 76, 103, 91 and 97.
Is the resistance greater than 10,000 ohms?
Yes No
GO to H35 .
REPLACE HO2S. REMOVE breakout box.
RECONNECT all components. RERUN Quick
Test .
Yes No
GO to H36 .
REPLACE HO2S. REMOVE breakout box.
RECONNECT all components. RERUN Quick
Test .
Yes No
GO to H37 .
REPAIR shorted circuit. REMOVE breakout
box. RECONNECT all components. RERUN
Quick Test .
H37 CHECK FOR OPEN HO2S HEATER GROUND HARNESS CIRCUIT
 Key off.
 Suspect sensor disconnected.
 Breakout box installed, PCM disconnected.
 Use the following list to measure the resistance between the appropriate test pins at the breakout box
and the HO2S HTR GND at the vehicle harness connector.

HO2S HTR-11 Test Pin 93 (HTR GND)

HO2S HTR-12 Test Pin 95 (HTR GND)

HO2S HTR-21 Test Pin 94 (HTR GND)

HO2S HTR-22 Test Pin 96 (HTR GND)
Is the resistance less than 4.0 ohms?
Yes No
Open or shorted or excessive resistance in the
heater circuit in the PCM. REPLACE PCM.
REMOVE breakout box. RECONNECT all
components. RERUN Quick Test.
REPAIR open or excessive resistance in the
heater circuit in harness. REMOVE breakout
box. RECONNECT all components. RERUN
Quick Test .