Advice on next steps: 07 pathfinder LX, 4-wheel. No start. Currently no communication with ECM, TCM, Display, HVAC, Air Bag, Steering Angle, or ABS. Scanner communicates with BCM, Seat Position, Meter,4-wheel,and IPDM. 1st dealer insisted on it being ECM, ECM had been tested by Module Experts. Purchased new ECM at their persistence, $1,500. Same issues, They then blamed in on water damage and the IPDM. I also purchased that new. Took to a 2nd dealer who found some broken wire in the CAN and K lines, repaired but only brought online a few more modules than before. They were at $1,200 in labor and Suggested I replace harness for $3,000. I quit and went back to DIY route, both engine room and front harness replaced with used harness. I took apart the old harness and traced out CAN bus circuit finding no issues. Still no communication with modules as listed above. I use the Harbor Freight Zurich diagnostics scope ZR Pro.

Currently read 60 Ohm on CAN Bus High to Low, and 120 when unplugging either ECM or IPDM. No shorts to ground or shorts to power that I can find on the CAN Bus. I show correct voltages on CAN bus, but scope shows some non-regular patterns (meaning CAN high doesn't always mirror CAN Low)... cheap Hantek scope. I get continuity to each branch back to the splices on the CAN (I took the dash apart to expose the main harness as well). I've checked power and ground to each of the modules. I've tried unplugging modules one at a time to see if I can discover a faulty module... I get continuity on the K-line. I suspect a faulty module some where, but how to find it ????

At my whit's end, but this has to be discoverable.

Sounds like you're in pretty deep so far, but you didn't provide any details about its history. Did you buy a salvaged vehicle? Based on your user name I'm going to take a wild guess that you purchased a car that had been completely flooded and declared a total loss by the insurer. Wrong or right?

Check the fusible links and contacts on the battery card. There are at least two that will crash everything in the engine box except the IPDM. If it's a steel key, also check the ignition switch. There are generally two "ignition" outputs and one will feed the engine box.

MisterH...logical guess, and I am in the insurance industry, but no, not a salvage vehicle. Never been under water to my knowledge, and yes I'm in deep... Too deep.

History: purchased used. Ran fine for 2 almost two years. Had loud muffler, that I ignored, this ultimately melted the rear harness to the fuel pump, rear lights, two rear ABS sensor wires,and some type of EVAP control located back there. We first replace fuel pump, before knowing the harness melted. The auto ran that way for a month or so but then suddenly quit. Replaced rear harness and full exhaust including all Cat's. Started and ran, but on test lost power and I limped home. It stared a time or two but never well. This all started my learning curve on this vehicle. Replaced APPS, TPS, the first IPDM in steps, then on to sending out ECM to module experts. They first claimed the ECM just needed flashed. When returned same symptoms. Back to them with more history, this time they replaced the ecm with a re programmed used ECM, same results. That is when I stated going to the dealers and spent the bigger bucks for same results.

Love my Pathfinder, but its been down now for most two years.

Will check battery card and report back. This has metal key with chip.. Will also check. ECM gets power to correct pins with ign switch on.

I'm no help with CAN Bus diagnostics yet I can't help thinking about how this might possibly be related to pin outs and harness differences. Awhile back I was helping a NICOclub contributor with an unrelated issue regarding his IACV and its wiring to the ECU on the same year Pathfinder I own. topic626565.html#p6807768
His confusion, and subsequently my own, was that the FSM for our '02 Pathfinders does not reflect the same wiring pin outs at the ECU or the same wire colors to our IACV connectors. To help him out, I pulled the junction connector off my ECU to verify this. Discovering that our wire harnesses to the ECU are built with a different wiring configuration than what is reflected in the FSM and that the ECU also had a different pin out than what is reflected in the FSM was a bit confusing. Nissan obviously made changes post publication of the FSM. Like I said, this is not specifically related to your issue but I can't help but wonder if there is some type of crossed up comms issue with your '07 now that you have replaced harnesses and the ECM. Like with my '02, I see multiple harness choices in part numbers for your '07, presumably different configurations, yet look the same on the outside. Same thing for the ECM. "Trust but verify" is the phrase that comes to mind.

Update. Nissan dealer has had the vehicle for two months now. Same dealer who suggested replacing wire harness. Now says TCM is the communications issue and suggest replacing the valve body along with re-pin the ALDL connector. Are ALDL's still used on the 07 pathfinder? Is there a schmatic? They want $1,800 but can only give me 80% assurance this is the issue? The Tech won't talk to me, only the dealer rep. Don't think they like me much.

Riskyplan wrote: ↑

Wed Oct 20, 2021 6:00 pm

Update. Nissan dealer has had the vehicle for two months now. Same dealer who suggested replacing wire harness. Now says TCM is the communications issue and suggest replacing the valve body along with re-pin the ALDL connector. Are ALDL's still used on the 07 pathfinder? Is there a schmatic? They want $1,800 but can only give me 80% assurance this is the issue? The Tech won't talk to me, only the dealer rep. Don't think they like me much.

I doubt the harness, but on RWD Nissans with the TCM inside the Valve Body, it's very common for crashed TCM's to bring down the whole CANbus or only let a few systems communicate. We see several every year. It's practically a ritual with no-start Fronties and Pathies and Xterras. The moment we see missing systems on a CAN scan, we pull the tranny connector to see if everything else wakes up. More often than not, it does.

PS - Sorry it didn't occur to me on my first response, I was thinking general CANbus maladies and not a specific model. I'm sure if I'd had your vehicle in front of me, the first thing I would have done was crawled underneath with a screwdriver to pop the tranny umbilical.

This is an interesting case study and sorry, I know at your expense. These issues are starting to become quite common today as vehicles age, involved in accidents and as mentioned water. Did you ever figure out what the problem was? I was curious when you said that the can bus signals were not right on the scope, and you discarded it because of the cheap scope.

Hantek may have some cheap scopes, but they also sell high quality units. I believe the reason the Hantek automotive scopes are cheaper is because they trying to get their product into the market.

CAN Bus shortages are beginning to appear more commonly, and we are seeing mechanics performing the same repairs and replacements that you have demonstrated, with no resolve. When asked if they viewed the CAN bus signals on a scope ......... the response is ........ what?

Scopes frankly can't tell you much about a CANbus other than whether the signals have integrity (i.e., not flatlined or swamped by noise) and are operating at the proper voltage. OEM's don't generally publish address and package info, or even simple bit rates. So while you can figure a lot out using SAE specs and publications if you want to dig, from a service diagnostic standpoint, scopes and sniffers are all pretty irrelevant.

Partial communication, where some devices can't talk or can only talk intermittently, is almost always the result of a power failure, internal failure of a device, or open wiring. So once power is ruled out, the best diagnostic is generally to disconnect devices one by one to see what wakes up, and if nothing does, then and only then start chasing the wiring.

The original author mentions he lost communication with several nodes in the CAN Bus system. This can be a symptom of a single shorted node, wiring connector/harness connected to the Can Bus. If such a short exists, the scope can be used to easily find if the system is shorted. There are five shorts that we are starting see. CAN Hi to ground, CAN Hi to power, CAN Lo to ground, CAN lo to power, CAN Lo to Hi. The scope will identify what type of short is occurring because all five shorts have a specific pattern. Once you know there is short then start the process as outline in your last statement. If splice joints exist and are accessible using a Network Isolator can save you a lot of time. The nice thing also about the scope is that you are observing the scope while disconnecting nodes and harness connections and will see immediate results if you isolate the CAN Bus away from the short.

Any sort of short circuit will show up with a simple voltmeter. Even a CANH/CANL short will show up as a "no traffic" situation with equal voltage on both legs, and a subsequent probe with an ohmmeter will reveal 0 ohms between the legs. The only condition which can't be diagnosed with voltage is a "crazy" device monopolizing the bus with constant traffic, which is a real-world condition we often see with the dead TCM's mentioned above. The only diagnosis which will work for that is to disconnect the offending device.

The real diagnostic problem these days is CAN gateways, with multiple separate buses being used in the car. Starting with the gen2 Rogues in (I think) '17, the typical late model Nissan has 3~6 discrete buses and none of them are accessible through the DLC connector. In fact, the DLC will show a "no traffic" condition at all times unless a scanner is connected in order to create some traffic. Regardless of whether a meter, scope, or sniffer is employed, the subordinate buses must all be accessed at the gateway or one of the subordinate devices. There's no provision for easy access, so some disassembly is always required just to get at the wiring, and troubleshooting is pretty much impossible without both complete documentation and a scanner capable of accessing the gateway. Be prepared for a struggle no matter what tools you use.

Agree on the voltmeter but prefer a scope:) I didn't realize 2017 Nissan incorporated a gateway. It's a whole other animal. Great information!

It started in '17, but now pretty much everything in the Nissan line has at least a 3-channel gateway. It's actually a very good idea for a reason few people think about -- hacking. In cars without a CANbus gatekeeper, it's actually possible to hack into the AV Unit or TCU (which are necessarily exposed to the outside world) and send out "spoof" commands pretending to be the ECM, ABS, or any other critical module. In a car capable of self-steering and self-braking, the potential to drive someone you don't like off a cliff should be obvious. The CAN gateway serves as a natural policeman between the AV/IT bus, which contains all the stuff connected to the outside, and the rest of the car's governance. So while the gateways admittedly complicate the s#it out of diagnosis, I'm not complaining about them. They're positively necessary in this new environment of machine-aided driving.