Pathfinder's No-Start Real Diagnostic PuzzlePosted 09/10/2004
By Tom Kolyer
The call came in on a 2000 Nissan Pathfinder equipped with a myriad of aftermarket accessories, including a 20,000-watt sound system complete with duct-taped connections. The technician explained that the car started cold, always drove great and never died on the road. There were no codes in the electrical control unit (ECU) and no fuel pulse. The last shop that had worked on the car replaced the main engine relay, the igniter, coils, plugs, fuel pump, fuel filter and a factory catalytic converter. The no-start problem only seemed to occur on a hot day when the car's owner played 18 holes of golf but not on a short nine.
I took into account that since this call came from Arizona, where it can be 110 degrees in the shade, a hot interior might play a role here. It could also be an anti-theft immobilizer issue. A factory security light was lit on the dash. When I inquired about the key, the technician said the car had a plain brass key and a well-used one from the original equipment manufacturer (OEM). Given these conditions, it should not have started at all with this key.
After much debate, we determined this car had a remote start setup. There were no keys or transponder chips taped or glued near the ignition lock cylinder or on the column cover. At this point, the technician went on to verify that no one had bypassed the theft deterrent signals. I suggested getting all the vehicle's keys as well.
A few days later, the second call came in. The technician had new information: The car had been bought at an auction and there were no other keys; plus, it had been in a wreck. Since our last conversation, the technician had removed the aftermarket remote start components and connected all the affected wires together. The car wouldn't start at all. Since it was running when it came in the first time, none of this made sense. He told me the security light was on solid. He had the dash out, and in the process turned on the antilock brake system (ABS) and supplementary restraint system (SRS) warning lights. I suggested he reset those lights.
At least now we knew that the theft deterrent system was part of the problem. All the wires tested good, all necessary components were in place and no key was taped into the column cover or the lock cylinder. The tech installed a used ECU, an ignition lock cylinder assembly with a matched transponder key - and the car started. (Note: This system normally requires programming of the ECU in the car to match all components in the system. Since these components were from a well-running vehicle and were changed in a matched set, it didn't need to be programmed.)
A week later, the tech called with a new problem: the car started hot but not cold. Let's recap: On the first call, the problem was a no-start hot and good-start cold. On the second call, the car never started. All parts of the system were changed and the harness continued to test well. The security light was always on during a no-start, and the suspected immobilizer problem continued.
The technician gained access to all the connections again but couldn't re-create the no-start. I asked him to check the lower dash panels and the column cover since those were the only items he removed. Upon close inspection, he remarked that the column cover was a piece of junk that was cracked and would need repair - just like the last shop had attempted. I asked him for more details. He told me that there was epoxy inside, near the lock cylinder. I asked him if he could chip any of it away. Once he started chipping, he found that an old key had been used to reinforce the repair.
Now the diagnostic puzzle was complete. Originally the column cover heated up, moving the glued key away from the receiver. This created no transponder recognition and a no-start. When cold, the column cover did not expand, and the anti-theft system worked fine. With the new lock cylinder installed, the opposite happened. When cold, the old transponder key excited the receiver and voila - a no-start. When warm, the new transponder key excited the receiver and the vehicle started.
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