2003 Murano, Crank no Start, no ECU Comms after changing Fan

[walczyk]

This is so upsetting. I had a bad radiator fan so I swapped both. I remember it was a tight fit, and some coolant poured out. I had to push the battery around to fit the fan shroud back down. I went to start to car and it was dead. The positive terminal was loose. I tighten it up and now its a crank no start. My code reader can't communicate, it can't "establish a link" and the radiator fans turn on blast which apparently is a failsafe mode sign when the canbus is down. How do I go about diagnosing this? The first step is powers and grounds to the ECU I guess, but does anyone have better advice on where to check in the FSM? I have to use PG to find the connectors, EC-151 is where the ECU powers and grounds testing starts, and then I have to go into the LAN manual I guess. I've never done CANBUS stuff before, so the more advice the better! This is a serious undertaking but I'd love to revive this car. Thank you!

[VStar650CL]

Check the EGI fuse in the IPDM, it may have blown when you fiddled with the battery. If not, you may have blown up the ECM. When a loose hot terminal sparks when trying to crank, it's a 200 amp spark with about two and a half kilowatts of energy. The voltage can exceed 18kV, and if it travels down the ECM supply wires and melts the protection diodes inside the ECM, the ECM is toast. That's actually a common occurrence in R51 Pathies, Frontiers, and Xterras simply because there's no loop in the ECM power wires to help dissipate the energy as RF. However, it's simply less common in Muranos and Maxes where the wires are looped, it can still happen if the spark is energetic enough. So if you find all your fuses are good, chances are your ECM is fried.

[walczyk]

Check the EGI fuse in the IPDM, it may have blown when you fiddled with the battery. If not, you may have blown up the ECM. When a loose hot terminal sparks when trying to crank, it's a 200 amp spark with about two and a half kilowatts of energy. The voltage can exceed 18kV, and if it travels down the ECM supply wires and melts the protection diodes inside the ECM, the ECM is toast. That's actually a common occurrence in R51 Pathies, Frontiers, and Xterras simply because there's no loop in the ECM power wires to help dissipate the energy as RF. However, it's simply less common in Muranos and Maxes where the wires are looped, it can still happen if the spark is energetic enough. So if you find all your fuses are good, chances are your ECM is fried.

s*** wow! There's no great of showing the ECM is fried other than verifying the powers and grounds and also using a scope to see the canbus is clean? Would unplugging the ECM bring back the OBD2 codes or no because that is in the ECM? Do you know the procedure for swapping an ECM? Do I need a consult ii tool/need to bring it to a dealership? Do you know anywhere that talks about programming with an aftermarket tool like this one? https://www.amazon.com/Piasini-Engineer ... B08FWZNCVM

[VStar650CL]

On an '03 there are several other systems on the car which should be on the CANbus (transmission, ABS, cluster, BCM, IPDM at the very least), so a look with a better scanner should tell you if any of those other systems are present. If any are, then it's an ECM problem and not a bus problem. The ECM needs to turn itself on and off by way of the ECM Relay located in the IPDM, so checking power to it can be complicated. It's arranged that way so the ECM can wake itself up to check the fuel tank when the car is parked. So checking for output at the IPDM is probably as good as you're going to do. If you look at the wiring diagram on PG-8 you'll see the ECM Relay. Fuse #82 is the ECM supply (IPDM layout on PG-44). Use a bulb-type test lamp for these tests, we're checking a power circuit and a voltmeter won't tell you if a circuit can carry power. First, make sure fuse #82 lights the light on both sides of the fuse with the key on. If only one side lights, you blew the fuse. Also check fuse #3 in the cabin fusebox, that's the ECM battery supply. If the fuses are good, see if pin 33 Red/Black and 35 Red on the IPDM light up with the key. If they do then the ECM has power but might have a blown CAN driver. If they don't, then move the test light gator to battery+ instead of ground and check if pin 44 White/Black lights up with the key. If it doesn't then the ECM isn't waking itself up and is probably blown.

I don't know anything about that Paisani scanner. The main thing that needs to be done when replacing an ECM is re-registering the keys. Once that's done the car should start (but may run crappy). Then you should do a Closed Throttle Position learn (CTPL) and Idle Air Volume learn (IAVL). If you have the CVTz50 app for your transmission then it has work support for those operations, or there are manual procedures for both (although doing IAVL manually is a bit of a PITA). If you want to get a used ECM, you need to go by the Hitachi part number on the outside of the box and it needs to match exactly. On an '03 it will be in the format MEC??-???, and all the question marks need to match, close doesn't count.

[walczyk]

On an '03 there are several other systems on the car which should be on the CANbus (transmission, ABS, cluster, BCM, IPDM at the very least), so a look with a better scanner should tell you if any of those other systems are present. If any are, then it's an ECM problem and not a bus problem. The ECM needs to turn itself on and off by way of the ECM Relay located in the IPDM, so checking power to it can be complicated. It's arranged that way so the ECM can wake itself up to check the fuel tank when the car is parked. So checking for output at the IPDM is probably as good as you're going to do. If you look at the wiring diagram on PG-8 you'll see the ECM Relay. Fuse #82 is the ECM supply (IPDM layout on PG-44). Use a bulb-type test lamp for these tests, we're checking a power circuit and a voltmeter won't tell you if a circuit can carry power. First, make sure fuse #82 lights the light on both sides of the fuse with the key on. If only one side lights, you blew the fuse. Also check fuse #3 in the cabin fusebox, that's the ECM battery supply. If the fuses are good, see if pin 33 Red/Black and 35 Red on the IPDM light up with the key. If they do then the ECM has power but might have a blown CAN driver. If they don't, then move the test light gator to battery+ instead of ground and check if pin 44 White/Black lights up with the key. If it doesn't then the ECM isn't waking itself up and is probably blown.

I don't know anything about that Paisani scanner. The main thing that needs to be done when replacing an ECM is re-registering the keys. Once that's done the car should start (but may run crappy). Then you should do a Closed Throttle Position learn (CTPL) and Idle Air Volume learn (IAVL). If you have the CVTz50 app for your transmission then it has work support for those operations, or there are manual procedures for both (although doing IAVL manually is a bit of a PITA). If you want to get a used ECM, you need to go by the Hitachi part number on the outside of the box and it needs to match exactly. On an '03 it will be in the format MEC??-???, and all the question marks need to match, close doesn't count.

Hey, so I found the dead fuse; number 82 but only after I missed it and pulled the ECM without unplugging the battery. I put a new fuse in and the ECM and now the car started up but the center console is COMPLETELY DEAD! I checked all the other fuses and they are good. What could I have done? The center console is just off and unresponsive, so there's no radio or climate control

[walczyk]

On an '03 there are several other systems on the car which should be on the CANbus (transmission, ABS, cluster, BCM, IPDM at the very least), so a look with a better scanner should tell you if any of those other systems are present. If any are, then it's an ECM problem and not a bus problem. The ECM needs to turn itself on and off by way of the ECM Relay located in the IPDM, so checking power to it can be complicated. It's arranged that way so the ECM can wake itself up to check the fuel tank when the car is parked. So checking for output at the IPDM is probably as good as you're going to do. If you look at the wiring diagram on PG-8 you'll see the ECM Relay. Fuse #82 is the ECM supply (IPDM layout on PG-44). Use a bulb-type test lamp for these tests, we're checking a power circuit and a voltmeter won't tell you if a circuit can carry power. First, make sure fuse #82 lights the light on both sides of the fuse with the key on. If only one side lights, you blew the fuse. Also check fuse #3 in the cabin fusebox, that's the ECM battery supply. If the fuses are good, see if pin 33 Red/Black and 35 Red on the IPDM light up with the key. If they do then the ECM has power but might have a blown CAN driver. If they don't, then move the test light gator to battery+ instead of ground and check if pin 44 White/Black lights up with the key. If it doesn't then the ECM isn't waking itself up and is probably blown.

I don't know anything about that Paisani scanner. The main thing that needs to be done when replacing an ECM is re-registering the keys. Once that's done the car should start (but may run crappy). Then you should do a Closed Throttle Position learn (CTPL) and Idle Air Volume learn (IAVL). If you have the CVTz50 app for your transmission then it has work support for those operations, or there are manual procedures for both (although doing IAVL manually is a bit of a PITA). If you want to get a used ECM, you need to go by the Hitachi part number on the outside of the box and it needs to match exactly. On an '03 it will be in the format MEC??-???, and all the question marks need to match, close doesn't count.

Sorry, I figured it out, I ended up using a fuse for the radio for the ECM and that's why the center console was dead. What was strange was that the radio fuse only had a connector on one side of the fuse. Current is running through one fuse leg; it's effectively just a jumper now. You're right I got to do the relearn procedure now; there's three of them I think, I've done it a few times from the FSM

[VStar650CL]

The connections on one side are usually a busbar, on the other side they're wire crimp terminations. So they don't generally look identical, the busbar side is just a metal slot. Glad you got it going and the ECM was okay!

[walczyk]

Thank you! The Nissan can be counter-intuitive with extra steps like having to manually start the idle air volume calibration, but I've been really impressed with how easy it is to work on

[VStar650CL]

Since you have a CVT, the slick option for doing IAVL and CTPL is to get an ELM327 bluetooth dongle and a copy of the CVTz50 app. In addition to monitoring your transmission, CVTz50 has very painless engine work support. Just be careful which dongle you buy, CVTz50 is fussy about it. The cheapest one I know about which works right is the VeePeak VP11, available for about $20 on eBay.