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Code P0236 - ideas? [Turbocharger back pressure (TCBP) sensor]

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62K views 24 replies 12 participants last post by  humblegeo  
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#1 ·
Howdy ST Nation! I need some advice..I have a 2013 ST, ~ 3500 miles on it. For about a week the yellow engine block icon has been glowing steadily. I called dealership, was told it was OK to drive, until my appointment Tues 5/28. Took it in, service manager told me it was showing a code P0236, indicating the Turbo Charger Back Pressure (TCBP) sensor was out of range. He further said this meant it wasn't giving me "that turbo oomf", but it was OK to drive. Now, the dealer is looking for a replacement TCBP sensor - to no avail! I've been told Ford has NONE available to ship from the factory, and that Ford wouldn't be interested in pulling any off the assembly line for a repair job. Apparently he's now put out a distrerss call nationwide to dealers to see if anybody can part with one for my car.

Very strange - how could Ford NOT have replacement parts? The service manager suggested the vendor who made the part had only made so many. Something lame going on here somewhere. In the meantime, the yellow engine block light stays on; I sometimes get the "Service engine now" message when starting up; when I do start up, that rightmost gauge on the dash pegs at 70 before settling down to a value of ~ 1/4 scale. Supposed to do that (hadn't noticed that before)?; the car's feeling sluggish; and the fun factor's taking a big hit.

Any thoughts? Foremost: think I'm damaging the car by continuing to drive it? Think the TCBP sensor is cause of sluggish feel? Anybody know of a black market in TCBP sensors? Thanks Nation - Bob :?:
 
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#5 ·
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#6 ·
Thanks SCrming (nice looking ride), Unreal for the link...Durp: The dealer called this AM and said they'd found the part in So Cal, it's being shipped today. I'll let you know after the install whether things are back to ST normal. Unreal, I had seen that thread pointing the finger at the wiring harness; Dealer said no way, not associated. We'll see ,huh?
 
#7 ·
Just to clear this up. It is the BOOST sensor, not the back pressure sensor. There are three sensors in the system which are used for a rationality check: barometric pressure, boost pressure and manifold air pressure. This code indicates that the rationality check failed, it is not indicating a voltage high/low condition. That could either mean that all 3 did not agree at key on; Baro and boost did not agree at small throttle positions; or Baro and MAP did not agree at wide open throttle.
 
#9 ·
Don't be too mad at your dealer about having trouble getting parts. Although I'd home and expect that over ten months into regular production service parts would be worked out, on a new car or model/powertrain it can take some time for parts to trickle into the service inventory, especially if it is something that doesn't fail often. Ford could very well be waiting on a batch from the manufacturer (which I'm curious if they're Bosch sensors and if so, there may be a comparable one that could work but your dealer and Ford isn't going to swap on aftermarket parts that aren't confirmed to work for your car).

As was mentioned that code appears to be for a rationality/sanity check the computer performs to make sure the sensors are performing correctly and as the computer would expect. Has the dealer tried to clear the code or have you disconnected the battery or used a scan tool to clear it? If they want to replace the sensor or sensors it shouldn't hurt but in the meantime if you clear it and it doesn't come back it probably isn't too serious of an issue for drivability.
 
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#10 ·
Thanks Eric. The service manager told me the tech did a continuity check on the sensor and in that way identified the problem. He said "it was just a little out of range"; I'll have to get clear on what "it" is (the sensor or that which it's monitoring).

I found this < P0236 FORD Turbo/Boost Sensor 'A' Circuit Range/Performance OBDII Engine Light Trouble Code | Engine-Codes.com > at another Focus ST site. Now I wonder whether the problem is correctly diagnosed and, dependent on that, whether I'm making things worse by continuing to drive it. I need to put about a 100 miles on it this weekend. Anybody know a mechanic who could give a competent 2nd opinion? I live in SF Bay Area (Union City). Thanks - Bob
 
#11 ·
I wouldn't have any issue driving it, especially if a dealer tech already cleared it as being okay until they can get a replacement. Even if the sensor were slightly out of range the stock wideband O2 sensor would allow the engine controller to ensure the fueling is still safe and the programming will probably fall back on other methods anyways even if one of the pressure sensors in the intake tract completely failed. Basically if the check engine light isn't flashing which would signifying possible severe engine or catalyst damage the car is safe to drive although it may not be performing optimally.
 
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#16 ·
The story continues



So, Nation, as it turns out, that wasn't the end of the story. After the TCBP sensor was replace and I started driving the St again, I *again* started getting "Service Engine now" messages (E29). Aaargh. Took it back to the dealer; dealer had to contact the Mothership ("Hotline"?) to get their opinion. On my document from the dealer: Call Hotline 106427921. Was told to inspect and view PIDS and wiggle test found sensor changed at S133 area. Inspect cannot see any bad wires. Advised Hotline on condition, was tol dto replace harness and retest. Installed new harness, check codes, none, Test drive and OK."

The harness replaced is FP Number Cu5Z-12A581-MA. I've had the ST back post-harness change since 6/28, so far so good.

- Bob
 
#18 ·
So to translate for anyone not able to read that, Ford's tech hotline advised the tech to plug in the scan tool and watch what sensor readings were doing while getting under the hood and physically wiggling the harness to watch for changes, such as those caused by shorts or bad connections in the harness or connectors. The S133 should be connector splice #133 where a sub-harness or major parts of the harnesses plug into each other.

When an intermittent wiring issue and bad connection is found, while it's possible to do continuity tests using a digital multi-meter or oscilloscope to watch waveforms of the sensor data to pinpoint which wire or connectors are at fault, if not done carefully it's easy to damage connectors when back probing them with test equipment and the labor would end up being more than Ford's cost to just replace that part of the harness. It's also pretty common for most automakers to just replace harnesses rather than risk taking a connector apart to repair a wire and/or pin in the connector and end up damaging something else depending on the specific harness (which is a bundle of wires and connectors).

Like a lot of repairs, there's specific troubleshooting procedures to follow to rule out possible components or issues. In your case it may have very well have been an intermittent wiring issue and the sensor that was previously replaced was actually not the problem and during the act of removing and replacing it temporarily caused the wiring problem to go away due to the harness being moved. At the time the diagnostics pointed to the sensor being the most likely source and if the harness wasn't acting up at the time they couldn't have easily figured out the symptoms would return. Hopefully this is a permanent fix and it shouldn't reappear.
 
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#19 · (Edited)
From the shop manual regarding P0236:

P0236 - Turbocharger/Supercharger Boost Sensor A Circuit Range/Performance

Description: This DTC sets when either of the following conditions are present.
When the throttle intake pressure (TIP_PRS_BOOST) PID does not correlate with the barometric pressure (BARO) and the manifold absolute pressure (MAP) PIDs at ignition ON.
When the turbocharger boost pressure (TCBP) sensor does not correlate with the BARO sensor at idle and the TCBP sensor and MAP sensor fail to correlate while driving.
Possible Causes:

Damaged turbocharger boost pressure (TCBP)/charge air cooler temperature (CACT) sensor
Contaminated or blocked TCBP/CACT sensor
Slow responding TCBP/CACT sensor

Diagnostic Aids: Check the intake air system for leaks and restrictions.
The TCBP/CACT sensor is a dual function pressure and temperature sensor located on the intake air tube between the charge air cooler (CAC) and the throttle body.
Application Key On Engine Off Key On Engine Running Continuous Memory
All GO to Pinpoint Test EA .
 
#20 · (Edited)
The ST is probably using the newer Bosch T-MAP sensors, meaning they integrate a thermistor (temperature variable resistor) to measure charge temps as well as the pressure via a conventional MAP (manifold absolute pressure) sensor. The operation described in the shop manual is a sanity/correlation check to make sure when the engine isn't running they are all reading the same pressure and it may factor in temperature of the sensor to calculate air density. Without the engine running an the turbo not pressurizing the air they should all read the same, if not it sets the check engine code that a sensor reading may be off (due to the sensor, wiring, etc.) If the sensor was bad during engine operations it wouldn't be surprising if another MAP-related code was set or pending.


For further reading on what the sensor is and what it measures:
http://www.bosch.com.au/content/language1/downloads/Map_Sensor_Purpose_and_Function.pdf
 
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#21 ·
I just had the code pop on me last night. Got up this morning and scanned it with my sxt scanner. I went ahead and cleared it. Started back up and the light stayed off.

If it comes back its going to the dealership. I do have an intake on it but I only used the pipe. Its got the stock air box and filter. I thought it looked a lot better. Do you guys think the dealer will give me issues?
 
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#22 ·
white79bu said:
If it comes back its going to the dealership. I do have an intake on it but I only used the pipe. Its got the stock air box and filter. I thought it looked a lot better. Do you guys think the dealer will give me issues?
Click to expand...
Mine did. Saw the green filter and threw up their hands. Called it an aftermarket intake until I explained to them why their tech was wrong.
 
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#25 ·
I have a 2014 Focus ST with 8000 miles on it and got the Engine Failure Service Now message one morning when I first started it up. I went ahead and drove it down the street and it was missing stumbling cutting out. I came back home shut it off looked at things and restarted it everything was fine with no engine light and running good. Then two or three days later got the message again and engine light locked in. It would run but felt slightly sluggish after that so took it to the dealer. He kept it 3 days and replaced the TCBP sensor. A week later so far so good. Disappointed at having issues already with only 8000 miles. Hasn't this same basic ecoboost turbocharged engine been used in most of the ford cars past few years??
 
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