Multiple sensor failures after carbon cleaning intake valves. Wire short?

[Ven Zoah]

I cleaned the carbon buildup on my 2017 Mazda CX5 recently. I made sure to mask off most areas and I guess some carb cleaner overspray reached some of the wiring/connectors. After letting the car idle and get up to temp, it suddenly shut off (no misfires or anything) and threw some codes.

The codes are:

• P0069 - Manifold Absolute Pressure - Barometric Pressure Correlation
• P0335 - Crankshaft Position Sensor A Circuit
• P0193 - Fuel Rail Pressure Sensor A Circuit High

All of these occured simultaneously and the car will not start. It cranks, but nothing happens. All other electronics still work in the car.

Would this be a short in the harness somewhere? The wires so far look all fine. Or do the actual sensors need to be replaced. Trying to avoid paying for a towtruck to bring it into a mechanic.

 

[CarpeDiem]

While this potential cause gets tiresome, the symptoms you describe could be caused by a faulty battery. Easy to check, have the battery load tested at an auto parts store like Autozone for free.

 

[Silly Wabbit]

Where did you spray? Before or after the MAF?
What product you used?

 

[Ven Zoah]

While this potential cause gets tiresome, the symptoms you describe could be caused by a faulty battery. Easy to check, have the battery load tested at an auto parts store like Autozone for free.

Car won't start, so I would need to be towed. The starter and all other electronics seem to work fine, including the audio system and amp at a decent volume. Could it possibly be the alternator?
All of the sensors that failed seem to be sensors connected to the part of the harness that is attached to the intake manifold, which was removed.

Where did you spray? Before or after the MAF?
What product you used?

It was after the MAF. The airbox, throttle body and intake manifold were removed and masked off/covered up during the cleaning. I used Gumout Carb/Choke & Parts Cleaner.

 

[cz5gt]

This carb cleaner say not recommended for fuel iniected vehicles. May be spray the harness connectors and sensors connectors with crc electric cleaner and try again?
If it is the connectors of course.
The crankshaft sensor error would prevent startup if I recall.

 

[Ven Zoah]

This carb cleaner say not recommended for fuel iniected vehicles. May be spray the harness connectors and sensors connectors with crc electric cleaner and try again?
If it is the connectors of course.
The crankshaft sensor error would prevent startup if I recall.

I'll try clening the connectors tomorrow. I took them off and they all look clean already with no corrosion though.

 

[Conrad 16.5]

What made you think that your car had carbon build up?

 

[Ven Zoah]

What made you think that your car had carbon build up?

Cold start misfires. Removed intake manifold and there was a ton of build up. This car has 107k miles on it. These cars aren't immune to this problem despite Mazda's marketing claims. Still better than my GTI though (makes sense with the turbo).

 

[ceric]

I have a '17. Now I can imagine what my intake valves look like...
Thanks.
Seems like the two cylinders on the left (in pic) are much worse than the other two on the right.

Yes, a faulty position sensor would prevent engine startup. It happened to my BMW years ago.

Maybe letting it sit and dry for a couple days. Problem could go away.

 

[Ven Zoah]

I have a '17. Now I can imagine what my intake valves look like...
Thanks.
Seems like the two cylinders on the left (in pic) are much worse than the other two on the right.

Yes, a faulty position sensor would prevent engine startup. It happened to my BMW years ago.

Maybe letting it sit and dry for a couple days. Problem could go away.

Yeah the intakes on the right were cleaned and the left is what they looked like before the cleaning.

Update: Had it towed to Mazda to get a diagnosis. They wanted to replace the entire harness and quoted $1290. They basically told me what I already knew. There is a wire causing a short. I just had it towed back to my house and I'm going to look for the damaged wire myself.

Tried looking for wire diagrams, but couldn't find any that show the engine emission harness. I will just have to tear back the shielding and test each wire for continuity.

 

[yrwei52]

Yeah the intakes on the right were cleaned and the left is what they looked like before the cleaning.

Update: Had it towed to Mazda to get a diagnosis. They wanted to replace the entire harness and quoted $1290. They basically told me what I already knew. There is a wire causing a short. I just had it towed back to my house and I'm going to look for the damaged wire myself.

Tried looking for wire diagrams, but couldn't find any that show the engine emission harness. I will just have to tear back the shielding and test each wire for continuity.

IMO any damages to the wiring harness after cleaning intake valves seems to be odd unless you did some physical damage to any “exposed” wires or connectors. May be you should consider to replace crankshaft position sensor itself and see.

 

[dunhillmc]

Seems like the issue comes from using a carb/choke cleaner on an engine without a carb/choke. there are tons of products for specicially made for intake valves; why did you choose to use this one?

 

[Jmaz]

IMO any damages to the wiring harness after cleaning intake valves seems to be odd unless you did some physical damage to any “exposed” wires or connectors. May be you should consider to replace crankshaft position sensor itself and see.

I agree. I don't see much chance of the cleaner causing this. More like physical damage . It seems odd that the CPS would fail but stranger things have happened. At least Mazda made it accessible on the side of the engine instead of having to remove the crankshaft pulley like on some vehicles.

 

[ruthrj]

Did you rotate the crank on the engine, and then treat only the intake valves that were seated closed? Was the crank rotated in the correct direction if done manually (sorry, can’t remember if that was clockwise or counter clockwise). Worried the crank could have been turned the wrong way or carb/choke cleaner ran down into the cylinders. Probably wouldn’t have started and ran until warmed up though…

I did this myself at around 70k miles on my ‘13, and there is a lot that could have gone wrong with physical assembly and disassembly of the intake manifold and throttle body. I used b12 Chemtool but siphoned as much back out of the intake before moving on to another valve. I don’t think I spilt a drop of solvent outside of the engine. Would have been hard to do tbh. Mazda dealer heard what you said and thought sure, I’ll replace the wiring, but I doubt that’s the cause.

Is the connector to the MAF sensor good and tight? Is the MAF sensor clean? Does anybody know where the MAP sensor is located? Wondering if carb/choke spray got on that and it’s screwing up the reading. P0069 is a code for disagreement on MAP sensor and barometric pressure readings. I could see that causing other codes.

 

[AVC]

I'd carefully look at the electrical harness around the intake runners and make sure you didn't pinch any wiring.

Also pretty quick to disconnect and reconnect the PCM electrical connectors--in case messing with the intake harness tugged on the PCM connectors. There is a lever on top of each connector that disengages them. Remove battery positive cable before messing the PCM connectors.

Worst case is tracing conductors from the sensors reported in the error codes above.

 

[cz5gt]

thats from my 2018. Probably same as above attached file.

 

[AVC]

What I don't have are the harness diagrams for engine control system

 

[Silly Wabbit]

So to recap..
Intake manifold removed
Intake valves were cleaned
Everything reinstalled
Car started, warmed, and then died
Car cranked but wouldn't start

Did I miss anything?
I would double check all connectors are seated, no frayed wires. Perhaps even unplug battery to reset things

 

[Ven Zoah]

I agree. I don't see much chance of the cleaner causing this. More like physical damage . It seems odd that the CPS would fail but stranger things have happened. At least Mazda made it accessible on the side of the engine instead of having to remove the crankshaft pulley like on some vehicles.

Would it really be that one sensor that is casuing a short to all the other sensors that are failing? I charged up the battery and tried starting it again and I have 27 codes now.

• P0010 - Crankshaft Position Actuator Circuit / Open Bank 1
• P0098 - Intake Air Temperature Sensor 2 Circuit High
• P0108 - Manifold Abolute Pressure/Barometric Pressure Circuit High
• P0118 - Engine Coolant Temp Sensor 1 Circuit High
• P0123 - Throttle/Pedal Position Sensor/Switch A Circuit High
• P0193 - Fuel Rail Pressure Sensor A Circuit High
• P0222 - Throttle/Pedal Position Sensor/Switch B Circuit Low
• P0327 - Knock Sensor 1 Low Bank 1 or Single Sensor
• P0335 - Crankshaft Position Sensor A Circuit
• P061B - Internal Control Module Torque Calculation Performance
• P2101 - Throttle Actuator Control Motor Circuit Range/Performance
• P0010 - A Camchaft Position Actuator Circuit / Open Bank 1
• P0069 - Manifold Absolute Pressure -
• P0098 - Intake Air Temperature Sensor 2 Circuit High
• P0108 - Manifold Absolute Pressure/Barometric Pressure Circuit High
• P0118 - Engine Coolant Temperature Sensor 1 Circuit High
• P0123 - Throttle/Pedal Position Sensor/Switch A Circuit High
• P0193 - Fuel Rail Pressure Sensor A Circuit High
• P0222 - Throttle/Pedal Position Sensor/Switch B Circuit Low
• P0327 - Knock Sensor 1 Circuit Low Bank 1 or Single Sensor
• P0335 - Crankshaft Position Sensor A Circuit
• P061B - Internal Control Module Torque Calculation Performance
• P2101 - Throttle Actuator Control Motor Circuit Range/Performance
• P0193 - Fuel Rail Pressure Sensor A Circuit High (Permanent)
• P0335 - Crankshaft Position Sensor A Circuit (Permanent)
• P0069 - Manifold Absolute Pressure - Barometric Pressure Calculation (Permanent)
• P061B - Internal Control Module Torque Calculation Performance (Permanent)

The weird thing is, when I hook up the OBD2 reader and put it in data stream mode, I get good readings from all of the sensors that are apparently failing.

 

[Ven Zoah]

So to recap..
Intake manifold removed
Intake valves were cleaned
Everything reinstalled
Car started, warmed, and then died
Car cranked but wouldn't start

Did I miss anything?
I would double check all connectors are seated, no frayed wires. Perhaps even unplug battery to reset things

Yeah I took it all apart again and sprayed contact cleaner in the connector housing, let it dry for a day in the hot weather, then I used a multimeter and checked a bunch of wires with a probing tool. All the wires have continuity.