Symptoms Of A P0108 Diagnostic Trouble Code
As I mentioned in the previous page... the fuel system (which is a speed density type) in your Chrysler (Dodge, Plymouth, etc.) car or mini-van needs to know how much load the engine is under.
The PCM gets this engine load info from the MAP sensor's vacuum readings...
So when the PCM receives a MAP signal that doesn't match the actual engine operating conditions... it's not gonna' want to play ball and you'll feel it in more ways than one.
When the MAP sensor fails, you'll see one or more of the following symptoms:
- Check engine light (CEL) is lit.
- DTC P0108 is registered in the PCM memory.
- Vehicle doesn't pass the state mandated emissions test.
- Bad gas mileage.
- Hard start and/or extended cranking time (after shut off).
- Black smoke coming out of the tailpipe.
- Hesitation when accelerating your car or mini-van.
- Rough idle.
- Engine stalls as soon as you let off the gas pedal.
Let's find out what are the common causes of a P0108 DTC, in the next subheading.
Common Causes Of A P0108 Trouble Code
The most common causes of trouble code P0108 are:
- A bad manifold absolute pressure (MAP) sensor.
- A broken MAP sensor connector.
- A problem in the sensor 3 or 4 wires. Specifically, a short in one of them.
- A worn out engine that has very low or uneven engine compression.
- A fuel pump that's failing and not supplying enough fuel volume.
- A timing belt that's been installed incorrectly (timing marks not lining up).
- A bad PCM.
Although extremely rare for this to happen... a bad PCM can also cause a false P0108 trouble code.
Troubleshooting DTC P0108
What's gonna make P0108 Manifold Absolute Pressure (MAP) Circuit High Voltage OBD II diagnostic trouble code (DTC) make sense... is to remember that the PCM sees the manifold absolute pressure (MAP) sensor (MAPS) stuck producing a high voltage signal that corresponds to an engine that seems stuck at high RPMs and/or a big throttle angle.
If you recall, from the previous page:
- The MAP sensor's voltage signal increases when the throttle plate opens and manifold vacuum is lower.
- The MAP sensor's voltage signal decreases when the throttle plate closes and manifold vacuum is higher.
Just to recap the info in this tutorial... remember, when a DTC P0108 is registered, the PCM sees the MAP sensor reporting a low intake manifold vacuum pressure (and thus receiving a high voltage MAP signal) when it knows, via other sensor inputs, that it should be reporting a higher vacuum pressure (and thus lower voltage signal).
Confused yet? Don't worry, the MAP sensor test is very, very easy. By manually testing the MAP sensor with a multimeter, you and I can find out if it's truly fried or not.
You can find the MAP sensor tests here:
- 3-wire MAP Sensor Test:
- MAP Sensor Diagnostic Test Chrysler, Dodge, Plymouth (at: easyautodiagnostics.com).
- 4-wire MAP Sensor Test:
- Chrysler 4-Wire MAP Sensor Diagnostic Test (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!