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.
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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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