I have had a steady engine service light. When I checked code first time, it came as 5-15, which is undefined. I reset ECU to clear code. Shortly after after starting engine, light came on again, but now it is blinking erratically. I rechecked code and it is now coming up 5-5, which is no failure detected.
Anybody have a clue as to what the problem is?

 

When posting a request for technical information, it is good to provide details such as model year, odometer reading, recent repair history, and any symptoms in addition to the numeric Diagnostic Trouble Codes. I'll guess your Maxima is a '99. Is that right?

All DTCs are four numbers and the first number is always 0 or 1. Your DTC is 0515.

 

Diagnostic Trouble Code 0515 points to a problem with the Exhaust Gas Recirculation Volume Control Valve.

The EGRVCV uses a step motor to control the flow rate of exhaust gases from the exhaust manifold into the intake manifold. Its operation is governed by pulsed signals from the Engine Control Module.

This malfunction is detected when an improper voltage signal is sent to the ECM through the EGRVCV.
Possible causes include ...
- Harness or connectors (The EGRVCV is open or shorted.)
- faulty EGRVCV

Check fuse #58 (10 amps), located in the narrow link and fuse box adjacent to the battery.

Relay Box #2 is immediately forward of the battery. The EGI relay is at the left front corner position (as seen from the front of the vehicle) of Relay Box #2. This is a type 2M relay and is in a brown plastic case. You may exchange the EGI relay with any of the other brown relays in Relay Box #2, as all brown relays are interchangeable.

The EGRVCV is located just below the throttle body. It is easy to see but not easy to reach. You may make some electrical tests on the EGRVCV "in situ" if you are dexterous, otherwise you will have to remove the EGRVCV from the vehicle.

Disconnect the electric connector from the EGRVCV. Looking into the connector cavity on the EGRVCV with the latch at the 12 o'clock position, there are two rows of terminals with three in each row. The upper row is numbered 1-3 right to left. The lower row is numbered 4-5 right to left. Measure the resistance between these terminal pairs ...
2 and 1
2 and 3
5 and 4
5 and 6
At 68 degrees F all resistance values should be 20.9-23.1 ohms.

If you found it necessary to remove the EGRVCV from the engine to make the resistance test you can also make one more test. Connect the electric connector. Have an assistant turn the ignition ON and OFF repeatedly (no need to start the engine). The EGRVCV shaft should move smoothly each time the ignition is turned ON and OFF.