Mechanics

SUBARU LEGACY TERMINAL PROBLEM

2003 Subaru Legacy • 100,000 miles

CODE 37 IN COMPUTER REPLACED REAR 02 THREE DIFFERENT ONES ALL WIRED DIFFERENT. CHECKED WIRING FROM COMPUTER DOWN ALL OHMS GOOD YELLOW RED WIRE 12 VOLTS HEATER CIRCUIT BLK WHT GROUND HEATER CIRCUIT WHIT SENSOR VOLTAGE WHT BLUE SENSOR GROUND
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Guest
October 30, 2012.



DTC P0037: REAR HO2S HEATER CIRCUIT, MALFUNCTION

DIAGNOSTIC PROCEDURE

1. Perform basic diagnostic procedure. Turn ignition off. Disconnect ECM connector B136 (26-pin connector). Using an ohmmeter connected to ground, measure resistance at ECM connector B136 (26-pin connector) terminals No. 5 and No. 16. See Fig. 10. If resistance is less than 5
ohms, go to next step. If resistance is not less than 5 ohms, repair open in appropriate wire between ECM and engine ground terminal.

2. Start engine. Using scan tool, observe rear HO2S heater current value. If current draw is not more than 0.2 amp, go to next step. If current draw is more than 0.2 amp, check for poor terminal contact in connectors between ECM and rear oxygen sensor.

3. Start and idle engine. Using a DVOM connected to ground, measure voltage at ECM connector B136 (26-pin connector), terminal No. 4. If voltage is less than one volt, go to step 6. If voltage is not less than one volt, go to next step.

4. Measure voltage between ECM connector B136 (26-pin connector), terminal No. 4 and ground while wiggling harness and ECM connector. If voltage changes to less than one volt while wiggling harness and connector, repair poor terminal contact in connectors. If voltage does not change to less than one volt while wiggling harness and connector, go to next step.

5. Turn ignition off. Disconnect electrical connector from rear oxygen sensor. Turn ignition on. Using a DVOM connected to ground, measure voltage at ECM connector B136 (26-pin connector), terminal No. 4. If voltage is less than one volt, replace ECM. If voltage is not less than one volt, locate and repair short circuit in wiring between ECM and rear oxygen sensor. After repair, replace ECM.

6. With electrical connector disconnected from rear oxygen sensor, measure voltage between rear HO2S connector terminal No. 2 and ground. See Fig. 11. If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between main relay and rear oxygen sensor.

7. Turn ignition off. Measure resistance across rear oxygen sensor connector terminals No. 1 and No. 2. If resistance is less than 30 ohms, locate and repair open circuit in wiring between ECM and rear oxygen sensor and check for poor terminal contact in connectors. If resistance is not less than 30 ohms, replace rear oxygen sensor. Clear memory and perform verification procedure.


KHLow2008
Oct 31, 2012.