Was driving on a main street when I hit the brakes for an oncoming speed bump. Car was driving completely fine with zero issues. Suddenly, as I'm braking, the engine turned off, all dash lights came up, and the brakes locked up. The most prominent thing was the small dash screen showing "PRNDL ERROR - NO BACKUP AID". It had power, the battery voltage was healthy, but zero cranking. The fuel pump wasn't priming when the ignition was on the switch position. The odo was showing dashed lines instead of numbers. Those dashed lines were also on the trip and estimated range computer. Also, an obd2 scanner I had around didn't see the PCM at all, saying to check the port connection and ignition switch position. I unplugged both battery terminals and left the truck to cool for a bit, but I got nothing different. I checked for any burnt or damaged harnesses near the battery and near the fusebox but found nothing. I checked the R203 relay (PCM, fuel pump) and it didn't seem to be burned, and also checked its 3 fuses (32, 33, 34) but they were all healthy. I switched this relay with one related to the trailer accessory but also got nothing. After checking everything I can on the side of the road, I called in a tow truck, and took it away. I first suspected the trans wiring harness to have an issue, but that odo issue and dead fuel pump shifted my focus to the fusebox. I'd assume that the fusebox isn't completely bricked since the lights, hazards, and dash lights and codes all worked normally. Not sure what the next step should be. Would really appreciate any support before I possibly send it to a shop
Sudden death
- Thread starter nabil
- Start date
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Mediamonkey11
Well-Known Member
If you have forscan, that'd be my next step to see if it at least sees the network and would tell you if your pcm is talking at all. Definitely sounds PCMish problems TBH
There are three plugs on the pcm, the transmission harness is the small one. It has all the transmission connections and the two rear oxygen sensors. This harness connects to the transmission range switch. Look under the car on the driver’s side and see if the connector is damaged at that transmission sensor. The car will not crank and start if the range sensor does not see park or neutral.
Thanks for asking. I sent it to an electrician eventually after running out of tests. He found the PSP switch wiring to be causing a short circuit in the harness, and said harness is connected to the main engine harness. After he insulated the wires and removed the bad connector, the truck started up nicely. He told me to get a new CKP connector and replace it since the one on it was loose. On the drive home I find the ABS and AdvTrac lights on the dash. Plugged in Forscan to find 10 unrelated ABS codes, so I knew something was up with the module itself. Unwilling to pay the electrician more, I ignored the ABS stuff. A few days later, I was driving on a highway when the engine shut off and all dash lights came up. Stopped, put it in neutral, and started up the engine with no issues. A minute later, it did the same thing. Kept shutting off on every tiny bump or turn on the road. I took the first exit and stopped. The issue became intermittent and dumb. Sometimes no cranking and the same PRNDL error, sometimes it cranked without igniting, and sometimes it started up but turned off after just moving the steering or operating any accessory. Went under the truck, moved around blindly that same PSP harness, and the car started when I cranked it, and it stayed on for longer than usual, so I drove it home. That drive was abysmal, as it would turn off suddenly but then start up, and it was popping and banging out the exhaust cause of unburned fuel. The next day, I changed the CKP connector with a new one, and the truck seemed perfect, until I took it to 80mph and braked, which turned the engine off, but it turned back on neutral in a stop. Went back home, turned it off, and it no longer started up, showing the PRNDL error again. The next day, it still wasn't turning on, but the fuel pump was priming. I disconnected the 3 PCM harnesses and cleaned the female and male sides with contact cleaner, and then the truck started. I moved the steering a few degrees and it turned off, and refused to come back to life. Forscan showed 'error' on the PCM, ABS, and RCM modules, and only read the OBDII protocol and the IC module. Any PCM-related tests also failed. I went under the truck to check that PSP harness. As I went up through it, I found 4 wires all removed of their insulation, so 4 individual copper strands touching each other. 3 were for the PSP and 1 for the oil pressure switch. I was amazed by how dumb this wiring is, so i cut off the oil pressure switch wire after failing to disconnect the connector, and took the harness up to the engine bay. Got new wiring to splice in. Hoping that's the only issue. If not, this truck will make my vacation real exciting. I attached the amazing wiring and the diagram of the shorting PSP and oil pressure switch wires.
Attachments
Update: I solved the shorting PSP and OPS wiring and renewed the entire harness branch. Now the truck always starts but dies immediately. When it dies, the dash throws out some random lights and codes, but then seems to reset, and the fuel pump begins priming again, all that without moving or cycling the key. As if the PCM loses communication then regains it by itself. What's interesting is that every time it takes the same amount of time to crank the engine, start, stall, and PCM to regain life. Replaced the positive battery terminal clamp because it was degraded but nothing changed. Inspected the grounds but all look healthy. I even jumped a wire from the negative battery terminal to the engine block, but nothing changed. Headlights and the blower motor keep working when the engine stalls, so power loss isn't universal. Forscan shows RPM readings when cranking, so the CKP is healthy. Forscan also loses communication when the engine stalls, but is reconnects almost immediately by itself. The KAM does not reset every time the engine stalls, so the PCM doesn't completely lose power on every stall. In the past, I was getting a P0620 (Generator Control Circuit Malfunction) code, but relatively ignored it. It doesn't appear now. However, when thinking of harnesses that have been moved around a lot, the battery to alternator harness is most prominent, as the battery was replaced very recently, and the technician who replaced it seemed forceful with the harness, and I myself moved that harness around when replacing the terminal clamp. That harness also moves a lot with engine movement. Would really appreciate any different ideas or what could've gone wrong with alternator wiring.
I know you said the grounds were good but,
From what you said in this post it really sounds like a lifted ground somewhere.
If you have a digital volt meter you could do a VOLTAGE DROP TEST to check all your connections on the battery cables.
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