ML63 AMG persistent engine warning light
Discussion
2008 car, M156 non turbo engine.
I have 2 error codes that I cant seem to remedy -
P0113 Air intake sensor short circuit to positive or an open circuit
P0071 Plausibility error between signal of temp sensor in intake pipe and outside temp sensor.
The car came with a decidedly Amazon looking sensor and a pair of similar quality flow meters.
I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
I have 2 error codes that I cant seem to remedy -
P0113 Air intake sensor short circuit to positive or an open circuit
P0071 Plausibility error between signal of temp sensor in intake pipe and outside temp sensor.
The car came with a decidedly Amazon looking sensor and a pair of similar quality flow meters.
I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
Agreed re the Amazon sensors.
Short circuit to positive would usually mean a missing or poor earth - it just means the signal is higher than expected
Open circuit is just that.
Plausibility sensor error means the reported sensor values don’t agree.
All of the above can be due to poor pin fitment on the corresponding connectors - caused by someone ham-fistedly pushing meter probes into the connector and spreading the pins. Which is quite probable if someone has used Amazon replacements for sensors.
Close examination of the connectors with a magnifying glass should show if this is the case.
Short circuit to positive would usually mean a missing or poor earth - it just means the signal is higher than expected
Open circuit is just that.
Plausibility sensor error means the reported sensor values don’t agree.
All of the above can be due to poor pin fitment on the corresponding connectors - caused by someone ham-fistedly pushing meter probes into the connector and spreading the pins. Which is quite probable if someone has used Amazon replacements for sensors.
Close examination of the connectors with a magnifying glass should show if this is the case.
swampy442 said:
The car came with a decidedly Amazon looking sensor and a pair of similar quality flow meters.
I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
As others have said, if they are non-genuine sensors that is always your first port of call.I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
Just because the sensor is showing resistance means basically nothing if the resistance it is reading is wrong.
Under these circumstances it is always best to start with the correct items & then clear the codes & see what happens from there.
After that, if there is still the same issue get a wiring diagram & check the readings at the ECU end of the sensor wiring & that will confirm both wiring & sensor.
swampy442 said:
2008 car, M156 non turbo engine.
I have 2 error codes that I cant seem to remedy -
P0113 Air intake sensor short circuit to positive or an open circuit
P0071 Plausibility error between signal of temp sensor in intake pipe and outside temp sensor.
The car came with a decidedly Amazon looking sensor and a pair of similar quality flow meters.
I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
Well obviously do some testing at the sensor wiring, apply a variable resistance if need be and see if the temp reading changes as expected.I have 2 error codes that I cant seem to remedy -
P0113 Air intake sensor short circuit to positive or an open circuit
P0071 Plausibility error between signal of temp sensor in intake pipe and outside temp sensor.
The car came with a decidedly Amazon looking sensor and a pair of similar quality flow meters.
I checked there was voltage at the plug, there was, checked the stock Mercedes sensor and the 'replacement' had both continuity and gave a resistance value, they did. If you go and check the live data the sensor shows -48 degrees, has anyone got any pointers?
Just to clarify the factory MB sensor was fitted, the cheapo was provided with the car.
Its going to be difficult to check the condition of the plug terminals due to the location (right down the back of the engine by the firewall) and the size as they're tiny but Ill have a look. And its a short length of wire the then buries itself in the main engine loom. I don't have a wiring diagram but checking the ECU pins is a good shout
Out of interest I fitted the cheapo sensor and the same results, within a couple of degrees
Its going to be difficult to check the condition of the plug terminals due to the location (right down the back of the engine by the firewall) and the size as they're tiny but Ill have a look. And its a short length of wire the then buries itself in the main engine loom. I don't have a wiring diagram but checking the ECU pins is a good shout
Out of interest I fitted the cheapo sensor and the same results, within a couple of degrees
swampy442 said:
Thing is, Im getting voltage at the plug, so I guess the break is in the earth line. I can check for continuity
Are you doing a proper load test passing a reasonable current through it, or just testing with a (very high impedance, obviously) multimeter? It will need about 0.2AYou ll have to excuse me, my trade and knowledge is jet engines not electrics. All the testing I've done is with a common or garden fluke, nothing fancy.
So checked the sensor temps on the code reader, -48 as before, sensor unplugged -48. Voltage read 4.980 volts sensor removed, 4.891 with it fitted so the ECU can see something.
Checked the voltage across the pins - 4.44v, now if I check the voltage to earth (from the power pin to the engine) it still reads 4.44v. So am I right in assuming that s an earth fault?
Also as an illustration here's the access. You can't actually see anything, especially to strip back the loom wrap, the loom goes round the engine and under the throttle body so looks like I'm stripping the manifold and firewall.
So checked the sensor temps on the code reader, -48 as before, sensor unplugged -48. Voltage read 4.980 volts sensor removed, 4.891 with it fitted so the ECU can see something.
Checked the voltage across the pins - 4.44v, now if I check the voltage to earth (from the power pin to the engine) it still reads 4.44v. So am I right in assuming that s an earth fault?
Also as an illustration here's the access. You can't actually see anything, especially to strip back the loom wrap, the loom goes round the engine and under the throttle body so looks like I'm stripping the manifold and firewall.
Edited by swampy442 on Friday 12th September 12:13
swampy442 said:
So checked the sensor temps on the code reader, -48 as before, sensor unplugged -48.
Sounds like the ECU is reading open circuit on the sensor.swampy442 said:
Voltage read 4.980 volts sensor removed, 4.891 with it fitted so the ECU can see something.
Where were those readings taken ECU or sensor end?swampy442 said:
Checked the voltage across the pins - 4.44v, now if I check the voltage to earth (from the power pin to the engine) it still reads 4.44v. So am I right in assuming that s an earth fault?
Where exactly were those readings taken ECU or sensor end?Next step would be to find a wiring diagram, it is needed for the next suggestions:
1) Find the ECU and determine which connector and wire the sense signal from the suspect sensor is. Then tap into this using preforably backprobes, failing that wire piercing probes. Do the same on the sensor end. Do a basic check of continuity (resistance should read not much more than a few ohms at most).
2) If there is a break then create a connection using your own wire, to bypass it, and use live data to confirm it can now read the temperature okay.
3) Carefully observe the wiring diagram and see if there's any splices or connectors along that circuit path. It would make sense to check at connectors first. In particular, check for corrosion.
4) Then visually observe the wire bundle, checking for physical damage, chafing, corrosion etc. A wire can internally break quite some distance from the connector due to the way corrosion works.
A bodge would be to simply tap in and run your own wire to join the break end-to-end.
1) Find the ECU and determine which connector and wire the sense signal from the suspect sensor is. Then tap into this using preforably backprobes, failing that wire piercing probes. Do the same on the sensor end. Do a basic check of continuity (resistance should read not much more than a few ohms at most).
2) If there is a break then create a connection using your own wire, to bypass it, and use live data to confirm it can now read the temperature okay.
3) Carefully observe the wiring diagram and see if there's any splices or connectors along that circuit path. It would make sense to check at connectors first. In particular, check for corrosion.
4) Then visually observe the wire bundle, checking for physical damage, chafing, corrosion etc. A wire can internally break quite some distance from the connector due to the way corrosion works.
A bodge would be to simply tap in and run your own wire to join the break end-to-end.
E-bmw said:
swampy442 said:
So checked the sensor temps on the code reader, -48 as before, sensor unplugged -48.
Sounds like the ECU is reading open circuit on the sensor.swampy442 said:
Voltage read 4.980 volts sensor removed, 4.891 with it fitted so the ECU can see something.
Where were those readings taken ECU or sensor end?swampy442 said:
Checked the voltage across the pins - 4.44v, now if I check the voltage to earth (from the power pin to the engine) it still reads 4.44v. So am I right in assuming that s an earth fault?
Where exactly were those readings taken ECU or sensor end?paul_c123 said:
Next step would be to find a wiring diagram, it is needed for the next suggestions:
1) Find the ECU and determine which connector and wire the sense signal from the suspect sensor is. Then tap into this using preforably backprobes, failing that wire piercing probes. Do the same on the sensor end. Do a basic check of continuity (resistance should read not much more than a few ohms at most).
2) If there is a break then create a connection using your own wire, to bypass it, and use live data to confirm it can now read the temperature okay.
3) Carefully observe the wiring diagram and see if there's any splices or connectors along that circuit path. It would make sense to check at connectors first. In particular, check for corrosion.
4) Then visually observe the wire bundle, checking for physical damage, chafing, corrosion etc. A wire can internally break quite some distance from the connector due to the way corrosion works.
A bodge would be to simply tap in and run your own wire to join the break end-to-end.
This is going to be the nightmare, to actually get at the loom. Ill have to look for an ECU pin out, and also see where the ECU is lol 1) Find the ECU and determine which connector and wire the sense signal from the suspect sensor is. Then tap into this using preforably backprobes, failing that wire piercing probes. Do the same on the sensor end. Do a basic check of continuity (resistance should read not much more than a few ohms at most).
2) If there is a break then create a connection using your own wire, to bypass it, and use live data to confirm it can now read the temperature okay.
3) Carefully observe the wiring diagram and see if there's any splices or connectors along that circuit path. It would make sense to check at connectors first. In particular, check for corrosion.
4) Then visually observe the wire bundle, checking for physical damage, chafing, corrosion etc. A wire can internally break quite some distance from the connector due to the way corrosion works.
A bodge would be to simply tap in and run your own wire to join the break end-to-end.
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