Yesterday I used a scan tool (purchased from ebay) and found two error codes in my ecu.

P0138 - 0510 (Downstream oxygen sensor maximum voltage monitor fault)
P0400 - 0302 (EGR insufficient or excessive flow detected)

I've read the stickies and found alot of useful information but I was wondering if some of you guys got these same error in the past and could share what you did to correct these problem. I'm not even sure if these are major problems... hope not. Thanks in advance for your help. I appreciate any and all feedback on this. Thanks.

 

Replacing O2 sensor should get rid of the 0302 code..if not, post back.

 

PO400-0302: 0302
Diagnostic Trouble code 0302 points to a problem with the Exhaust Gas Recirculation system. The malfunction is detected by the Engine Control Module when no EGR flow is detected under conditions which call for EGR. Possible causes include:
- The electrical harness or connectors (valve circuit open or shorted)
- The EGR valve is stuck closed
- Weak or dead battery
- The EGR passage is clogged
- Faulty EGR temperature sensor circuit
- A leak somewhere in the exhaust system

The EGR Volume Control Valve may be tested with an ohmmeter. Disconnect the electrical connector. Looking at the connector half which is attached to the EGRVCV with the latch at the 12 o'clock position you will see two rows of three terminals. The top row is numbered 1-3, right to left. The bottom row is numbered 4-6, right to left. Measure the resistance between these terminal pairs:
2 1
2 3
5 4
5 6
... all resistance values should be 20.9-23.1 ohms at 68 degrees F.

Reconnect the EGRVCV connector halves. Turn the ignition switch ON OFF repeatedly. Verify that the EGRVCV shaft moves smoothly forward backward according to the ignition switch position.

The Exhaust Gas Temperature Sensor may be tested with an ohmmeter. The specifications are ...
- at 32 degrees F, 0.68-1.11 Megohms
- at 122 degrees F, 0.09-0.12 Megohms
- at 212 degrees F, 0.017-0.024 Megohms

P0138 - 0510: 0510
Diagnostic Trouble Code 0510 points to a problem with the Rear Heated Oxygen Sensor. This sensor is mounted in the exhaust stream, just downstream of the Catalytic Converter. When the two Front Heated Oxygen Sensors are operating properly the Rear Heated Oxygen Sensor is not used for engine control operation. It is used to monitor the condition of the Catalytic Converter. If either or both Front Sensors fail the Engine Control Module uses the signal from the Rear Sensor to maintain a correct fuel/air mixture.

DTC 0510 is detected when the signal from the Rear Heated Oxygen Sensor does not reach the expected maximum voltage threshold value. The possible causes include ...
- Harness or connectors (the sensor circuit is open or shorted.)
- Rear Heated Oxygen Sensor
- Fuel pressure
- Fuel injectors
- Intake air leaks

 

I think you have that flipped...replacing the O2 sensor will take care of the 0510 code. :thumbsup;