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Z31 Injector Service Campaign Information

It's time to give a page about the fuel injector service campaign to help eliminate some of the confusion.

Nissan Voluntary Service Campaign - Fuel Injectors and Hoses.

    References: Fuel Injector Service Campaign PDF files
  • NTB96-010: January 18, 1996 (U11, Z31)
  • NTB96-010a: March 15, 1996 (U11, Z31)
  • NTB96-010b: March 18, 1996 (U11, Z31, F31, S12-V6)
  • NTB96-052: May 17, 1996 (S12-V6)
  • NTB96-010e: May 17, 1996 (U11, Z31)
  • NTB96-024: May 17, 1996 (F31)
  • SBN-004: May 17, 1996
  • NTB96-010g: August 28, 1996 (U11, Z31, S12-V6)
  • NTB97-035: April 30, 1997 (Z31)

MYTH: Nissan issued a recall on the fuel injectors for all Z31 model 300ZX cars.
FACT: Nissan issued a SERVICE CAMPAIGN for the fuel injectors on all US model 300ZX cars. What's the difference? Not a whole lot. Mostly legal terms and liability issues. Basically, Nissan doesn't have to actively search for the models that this campaign applies to. This makes it the owner's responsibility to have the car brought in to have the work done. It also helps Nissan say that they don't have to perform the work on any car that's been modified beyond a certain point. And various other legal reasons for them to worm their way out of paying for it on all cars. I understand the campaign work is sometimes done in Canada now. I haven't heard of any other countries that have been able to get it done.

MYTH: The Nissan dealer changed the ECU firing pattern.
FACT: The ECU is not touched during the injector work. Because of the condition of most of the cars that come in to get worked on, Nissan opted to install a new injector sub harness. Before the service campaign, the ECU had two firing modes, simultaneous and group. Simultaneous Injection mode means that all injectors fire at the same time. This mode is when the engine is over 3000 rpms, injection pulse duration is more than 6.5ms, or cylinder head temperature is below 60oC or 140oF. Group or Batch Injection mode means that the six injectors are divided into two groups. The groups are cylinders 1, 2, 3, and 4, 5, 6. These groups are fired once each engine cycle 180o opposite of each other. After the service campaign, the ECU still has both of these firing modes. The only difference is the groups. The new groups are 1, 3, 5 and 2, 4, 6.

MYTH: Before there were 6 seperate injector triggers and now there are only 2.
FACT:Before, there were 2 injector triggers. After there are 2 injector triggers. The only thing that's changed is the injectors they trigger. If you open the ECU, you will see th3 6 injector trigger leads. You can easily see on the board that the injector leads are connected just after the pins are soldered to the board. Pins 101, 102, and 103 all share the same trace all the way from the trigger to the pins. Pins 104, 105, and 106 all share the same trace all the way from the other trigger to the pins. The difference is now there is less physical wire that the signals have to travel through from the triggers to the injectors. Before there was approximately 6 feet of wire for each injector from the ECU making a total of 36 feet of wire. After there is approximately 6 feet of wire going to 2 injectors with about 6 inches from the center injector to each ajoining injector. The new total is about 14 feet of wire.

MYTH: I rewired my injectors back to the way they were, and my car ran better because of it.
FACT:If the car ran better, it was because there was a problem with the way the car was wired. There are two explanations.

  • The tech doing the service campaign screwed up and did a bad job connecting the new subharness making poor contacts.
  • The tech doing the service campaign screwed up and attached the subharness to the wrong attachment points.
    During the rewire, the original connectors are all cut off. The new subharnesses are then attached to the wires that originally went to injectors 3 and 4. Attaching the new subharness to the passenger side of the block should be very simple. If the crimps aren't made correctly, a large impedance can be created because of the poor connection. This will cause the ECU signals to not correctly get to the injectors. A new injector harness attached to the wires that originally went to 1 or 3 would not create a problem as one of the original groups contained both 1 and 3. The wires for injector 5 are very far back and very difficult to mix in with injector wires 1 and 3. Attaching the new subharness to the driver side of the block can be a bit more difficult. The injector wires that originally went to injectors 2 and 4 are very close together. If the tech doing the job cut the wires too short or isn't paying much attention, it's very simple to connect the new subharness to the original injector 2 wires rather than injector 4. Note that the injector 2 wires were also part of the group for injectors 1 and 3 that the other harness is attached to. If the tech accidently connects the driver side subharness to the injector 2 wires, the ECU now has one trigger driving all 6 injectors while the other remains quiet. Obviously this will cause a problem because the trigger was only designed to drive 3 injectors, not all 6.

    MYTH: I'm getting the service campaign done/I've gotten the service campaign done. I have to go back an rewire after they've "fixed" it.
    FACT: If the service campaign is done properly, you shouldn't notice any difference. If your car isn't running right when you get it back, take it back to the dealer and make them fix it. If you haven't had the service campaign done yet, take the service writer out to your car and make sure he/she knows that the car is running perfectly when you drop it off. Explain to him/her that it needs to be running just as well when you get it back. If they give you some comment about it, inform him/her that you have heard about many cars that have come back with problems because of going in to have the service campaign done. If you're still hesitant, ask them to NOT rewire the injectors. Explain that a great deal of confusion has come about because of the issues that appear to be coming from this step. Finally, if the car doesn't run right when you pick it up, don't accept it. Biggest thing: Don't sign anything until you drive it.