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Repair Toyota P0031 & Engine Light on

The Toyota Camry came back again for reparation, which had been repaired for several times because the CEL was on. Strangely enough, the car works well without other abnormalities.
Facing this thorny issue, this time I tended to apply V2014.6 Toyota Intelligent Tester 2 IT2 with Suzuki, the SUZUK company professional diagnostic tool for the Suzuki car. I first connected IT2 into the Powertrain / Engine and ECT / DTC, reading the error code P0031 (HO2S heater control circuit low), while the DTC's frame data found no error. According to the maintenance manual, the causes of P0031 are: A / F sensor heater circuit broken; A / F sensor heater (sensor1) fault; engine J/ B (EFI relay) fault; ECM failure, etc.

Toyota Intelligent tester 2

1) I disconnected C15A / F sensor connector to measure resistance of C15-1 and C15-2 terminal ( A / F sensor heater + B and HT terminals), reaches 2.6Ω, within the normal range (1.8 ~ 3.4Ω); moreover, resistance between C15-1 (HT) and C15-4 (AF-) terminals is infinite, normal. So A / F sensor failure can be excluded.
2) Then I turned on the ignition and measured voltage between the C15-2 (+ B) terminal and the bonding, which is 12.7V, normal. This will initially rule out the A / F sensor circuit fault.
3) According to the system circuit diagram, the resistance between C15-1 (HT) terminal and ECM C24-109 (HAlA) is 0.24Ω, and between C15-1 and the bonding is infinite, indicating that A / F sensor heater with ECM lines is normal. Considering that the fault occurred intermittently, I cleared the code and tested, however, CEL lighted again when the vehicle was driven on a relatively bumpy road.
4) Back to the shop, I found the code was still P0031 re-read by car diagnostic tool IT2. Then I entered Utility (Tools) / CheckMode, which will transfer ECM from normal mode to check mode, afterwards, shaking relevant components. When shaking J / B, CEL light up again. It turned up in several tests, so it can be determined as the J / B-related failures.
 Finally, I removed J / B and pulled 1E, the plug was found in corrosion. Combined circuit diagram, 1E-7 is the very power line of A / F sensor heater. I dealt with the corrosion, the fault was completely cleared after repeated test.

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