HEATED OXYGEN SENSOR NO. 1 HEATER CIRCUIT
If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuits are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction.
NOTE:Heated oxygen sensor No. 1 refers to oxygen sensor closest to engine block. Heated oxygen sensor No. 2 refers to oxygen sensor farthest from engine block.
NOTE:For component location, see appropriate illustration in THEORY & OPERATION article.
Heated oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to determine fuel injection system operation. DTC is set when heated oxygen sensor heater current draw exceeds 2 amps, or heated oxygen sensor heater current draw is.2 amp or less when heater operates. Possible causes are:
Heated oxygen sensor No. 1 heater circuit is open or shorted.
Defective heated oxygen sensor No. 1 heater.
Using scan tool, read freeze frame data. Freeze frame data records engine conditions when malfunction is detected.
Diagnosis & Repair
Access ECM in driver's side of engine compartment, next to battery. See Fig. 2. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 3 (Yellow/Red wire) at ECM harness connector E4. See Fig. 4. Voltage should be 9-14 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
Disconnect heated oxygen sensor No. 1 harness connector. Measure resistance between terminals B+ (Black/White wire) and HT (Yellow/Red wire) at heated oxygen sensor No. 1 (component side). See Fig. 6. Resistance should be 11-16 ohms at 68 F (20 C). If resistance is not as specified, replace heated oxygen sensor No. 1. If resistance is as specified, go to next step.
Repair wiring between ECM and heated oxygen sensor No. 1, and/or between heated oxygen sensor No. 1 and engine room junction box. See WIRING DIAGRAMS article.
Monday, February 2nd, 2009 AT 6:13 PM