Tech Tip: Nissan MIL On, DTC P0603 – ECM Power Supply – UnderhoodService

Tech Tip: Nissan MIL On, DTC P0603 – ECM Power Supply

If you have a vehicle with the MIL on that has a DTC P0603 stored in the ECM, perform the diagnostic steps in this bulletin first.

Applied Vehicles:
2006 Altima (L31)
2006-’07 Murano (Z50)
2006-’08 Maxima (A43), 350Z (Z33)
2006-’09 Sentra (B16), Frontier (D40), Xterra (N50), Pathfinder (R51), Titan (A60), Armada (TA60), Quest (V42)
2007-’09 Versa (C11), Altima (L32), Altima Hybrid (L32HV),
2008-’09 Altima Coupe (CL32), Rogue (S35)
2009 Maxima (A35), 350Z Roadster (Z33), Murano (Z51), 370Z (Z34), GT-R (R35)

Service Information:
If you have a vehicle with the MIL on that has a DTC P0603 stored in the ECM:
– Perform the diagnostic steps in this bulletin first.
– This DTC may have been stored due to a series of previous low battery voltage, dead battery or battery terminal disconnections. figure 1
– Do not perform any other diagnostic procedures or repairs for this code until you have performed the ones in this bulletin.
– See the Service Procedure in this bulletin for ­additional detail.

Service Procedure:
1. Connect Consult III to the vehicle. 

2. Turn the ignition to On, but do not start the engine. figure 2

3. Check for DTCs: (see Fig. 1)
– Confirm that DTC P0603 is stored. If P0603 is not stored, this TSB does not apply.
– If any additional DTCs are stored, document the DTCs before proceeding.

4. Erase all DTCs. Confirm that the engine has no DTC stored. See Fig. 2.

5. Turn off the ignition. Wait exactly 5 minutes after the display changes from “No DTC” To “Error.” See Fig. 3. figure 3
Note: This waiting period is necessary for the ECM to completely shut off. Do not disconnect either battery cable at any time during this procedure. 

6. Turn the ignition to On, but do not start the ­engine. Wait 10 seconds after the display changes from “Error” to “No DTC.” See Fig. 4.
If DTC P0603 does not display after the system check:Figure 4
• This will indicate P0603 was caused by a series of previous low battery voltage, dead battery or battery terminal disconnections.
• The vehicle harness, connections and ECM are operating properly. 
• Do not replace the ECM. No further action is necessary concering P0603.
• Go to step 9.
If DTC P0603 does display after the system check:
• Go to step 8.

7. Repeat step 5 and 6 five more times to complete the system check.

8. Refer to the appropriate electronic service manual for further DTC P0603 diagnostic assistance.

9. If other DTCs were previously stored, refer to the appropriate electronic service manual for further ­diagnostic assistance for those DTCs.

Courtesy of Mitchell 1.

You May Also Like

It’s Got Spark!

Why can’t you trust some spark tests?

You have probably seen some reality TV shows where the “builder” will pull a spark plug wire to confirm they have spark. This is one of the most misleading tests for the ignition system. If the spark plug produces a spark, the spark is at 14.6 psi (normal air pressure at sea level), not 170 psi or more inside the cylinder during the top of the power stroke.

Why Alternators Are Subject To Ripple Voltage

The alternator produces an AC current that must be converted into DC current by way of a rectifier.

ECM Damage

Engineers have devised two strategies that can be called the “immune system” for the electrical system.

Voltage Drop Testing

The measurement of voltage is like the speed of the traffic.

Spark Plug Fouling

Understanding why spark plugs get dirty.

Other Posts

Forcing OBD II Vehicle Emission Monitors

Some vehicles have readiness issues when it comes to setting all the OBD II monitors.

Auxiliary Water Pump Diagnostics

A car or truck comes into your shop with a complaint of poor heater performance- the issue may be the auxiliary water pump.

GM No Crank After Auto-Stop Event

These concerns could be caused by a broken or loose engine ground cable/strap, which grounds the engine to the body.

Hybrid Vehicle Fluid Maintenance

There are opportunities your shop can’t pass up just because the car or SUV has a hybrid badge on the back.