Car shut off while driving, possible wiring issue???

aaronkealoha

aaronkealoha

Greenie N00B Member
So I drove about 4 hours last night to visit my parents for the 4th of July, didn't have any serious issues. I had 2 codes for my o2 sensors (p0133 and P0138 I believe) that came on and off and then a lean at idle code (probably caused by o2 sensors not communicating well), but i was too worried about running lean because the AFRs looked fine on the freeway.

TODAY, I started the car, let it warm up, and was driving to meet my brother. Made it about 3 blocks and the car shut off, now won't start. I'm now stuck in an empty bookstore parking lot in a college town where the property owner has told me to hurry up and leave 3 times already. I've got a P0340 code (camshaft position sensor circuit malfunction) which I think is causing code U2023 as well.

My question is how do I go about looking for the wiring issue here? Do the o2 sensor codes give me any hint to where the short could be? Is there any major wiring harnesses that could have come off? I got screwed over by a Ford dealership that I took the car to to get the timing done, and ended up putting a new engine in myself; long story short is that there's a couple things I missed and I'm hoping that this is just a wiring connection that is loose somewhere.
 
Alright so it sounds like you have multiple issues going on at the same time so I'll try to break each one of them down.

The O2 codes can be set by an actual issue with the engine such as running lean. They can also be set by bad wiring or a bad sensor. Usually it is the sensor itself that is bad but it doesn't hurt to check fuel pressure on the low side going into the pump. If you have a scan tool or Accessport you can see what the HPFP is doing/putting out. Idle should be at least 400-500 on the high side and on the low side about 50-70 psi. Low side can also be checked before cranking if you let it sit for a bit as the HPFP reading should be whatever key on engine off pressure is (fuel pump priming)

Second is your cam sensor code. That really depends on what the code description is. It could be an actual timing issue or broken camshaft (highly unlikely but still a possibility) or it could be a wiring issue. The cam sensor is going to have I think 3 wires. A 5 volt reference, a ground, and a signal back to the ECU. Ideally you would check for 5V between the 5V and ground, then check resistance of the ground wire to actual ground, and finally check resistance of the signal wire between the sensor and the ECU. If the wires have higher than 2 ohms then there is an issue with the wiring. If that all checks out the sensor could be bad.

However make sure to check mechanical timing as well. Turn it to TDC and make sure the cam slots align with the back of the head. If one tooth is off it would be noticable.
 
L337TurboZ said:
Also when you said it won't start you didn't specify if it cranks but won't start or it won't crank at all.

Here is a link to a post about doing electrical diagnostics if you aren't familiar with using a multimeter or checking circuits

https://mazdaspeeds.org/index.php?threads/how-to-diagnose-thread.12295/
Click to expand...
Thanks a ton for the extra info, I'll go through that thread for sure. I got the car towed and got a multimeter so hopefully I can figure this out now.

As a reply to other questions... car still cranks but won't even get close to starting up. Was driving normally up until that point where it just completely shut off

L337TurboZ said:
Alright so it sounds like you have multiple issues going on at the same time so I'll try to break each one of them down.

The O2 codes can be set by an actual issue with the engine such as running lean. They can also be set by bad wiring or a bad sensor. Usually it is the sensor itself that is bad but it doesn't hurt to check fuel pressure on the low side going into the pump. If you have a scan tool or Accessport you can see what the HPFP is doing/putting out. Idle should be at least 400-500 on the high side and on the low side about 50-70 psi. Low side can also be checked before cranking if you let it sit for a bit as the HPFP reading should be whatever key on engine off pressure is (fuel pump priming)

Second is your cam sensor code. That really depends on what the code description is. It could be an actual timing issue or broken camshaft (highly unlikely but still a possibility) or it could be a wiring issue. The cam sensor is going to have I think 3 wires. A 5 volt reference, a ground, and a signal back to the ECU. Ideally you would check for 5V between the 5V and ground, then check resistance of the ground wire to actual ground, and finally check resistance of the signal wire between the sensor and the ECU. If the wires have higher than 2 ohms then there is an issue with the wiring. If that all checks out the sensor could be bad.

However make sure to check mechanical timing as well. Turn it to TDC and make sure the cam slots align with the back of the head. If one tooth is off it would be noticable.
Click to expand...


The two o2 sensor codes were high voltage and a slow response, which made me think it was a wiring issue. But it confused me since those codes went away and the lean at idle one stayed. On top of that, my fuel trims are all over the place, especially idling. LTFT is around 6 at idle and STFT is in the 20s. Would that be caused by the O2 sensors not giving a correct reading or would it be the other way around?

For the Fuel pressure, everything looked fine. I was watching it on my accessport for the entire drive yesterday, and it went up around 1800 when I was accelerating and stayed around 400 at idle, which is fairly normal from what I've read.
 
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aaronkealoha said:
The two o2 sensor codes were high voltage and a slow response, which made me think it was a wiring issue. But it confused me since those codes went away and the lean at idle one stayed. On top of that, my fuel trims are all over the place, especially idling. LTFT is around 6 at idle and STFT is in the 20s. Would that be caused by the O2 sensors not giving a correct reading or would it be the other way around?

For the Fuel pressure, everything looked fine. I was watching it on my accessport for the entire drive yesterday, and it went up around 1800 when I was accelerating and stayed around 400 at idle, which is fairly normal from what I've read.
Click to expand...

STFT at +20% means it could be a decent vacuum leak which is the most likely concern. The O2 sensor high codes could be due to the lean condition. If the engine is very lean it means the sensors are reading lean. The computer itself isn't sure if the sensor is bad or if there is an airflow problem, just that they are reading a higher voltage for a longer time than they should.

Check all of your hoses, clamps, couplers etc for a possible leak. Even something as simple as a loose air filter on a cold air intake can throw off fuel trims. I had a filter slip off one time which allowed just a little more air than what my MAF calibration was set at. It caused the car to run slightly leaner. Didn't throw a code but could feel a subtle skip.
 
L337TurboZ said:
STFT at +20% means it could be a decent vacuum leak which is the most likely concern. The O2 sensor high codes could be due to the lean condition. If the engine is very lean it means the sensors are reading lean. The computer itself isn't sure if the sensor is bad or if there is an airflow problem, just that they are reading a higher voltage for a longer time than they should.

Check all of your hoses, clamps, couplers etc for a possible leak. Even something as simple as a loose air filter on a cold air intake can throw off fuel trims. I had a filter slip off one time which allowed just a little more air than what my MAF calibration was set at. It caused the car to run slightly leaner. Didn't throw a code but could feel a subtle skip.
Click to expand...


that makes sense. I'll go through the vacuum lines tomorrow and search that out. I'll also keep testing the wiring tomorrow morning and hopefully it's nothing major. I'm going to hope that it is a wiring issue and not a timing issue though... I had to do it once on the last engine and once on this engine and I'm starting to get bored of it, as well as more and more scared that I'm going to mess it up lol
 
aaronkealoha said:
So I drove about 4 hours last night to visit my parents for the 4th of July, didn't have any serious issues. I had 2 codes for my o2 sensors (p0133 and P0138 I believe) that came on and off and then a lean at idle code (probably caused by o2 sensors not communicating well), but i was too worried about running lean because the AFRs looked fine on the freeway.

TODAY, I started the car, let it warm up, and was driving to meet my brother. Made it about 3 blocks and the car shut off, now won't start. I'm now stuck in an empty bookstore parking lot in a college town where the property owner has told me to hurry up and leave 3 times already. I've got a P0340 code (camshaft position sensor circuit malfunction) which I think is causing code U2023 as well.

My question is how do I go about looking for the wiring issue here? Do the o2 sensor codes give me any hint to where the short could be? Is there any major wiring harnesses that could have come off? I got screwed over by a Ford dealership that I took the car to to get the timing done, and ended up putting a new engine in myself; long story short is that there's a couple things I missed and I'm hoping that this is just a wiring connection that is loose somewhere.
Click to expand...
Did you ever find out what all this was?
 
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