P103 on my 2002 Ford Focus SE
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Check and clean the MAF wiring and connector and check for loose wires as you may have stretched/pulled the MAF wiring while working on the coil. If the MAF connector and wiring look in good shape, the code points to MAF sensor hardware failure. You can use a multimeter to backprobe the voltages at the MAF connector.
Sample testing procedure here: http://easyautodiagnostics.com/ford_maf/maf_sensor_ford_1.php
DTC code details:
P0103 - Mass Air Flow (MAF) Circuit High Input
The MAF sensor circuit is monitored by the PCM for high air flow (or voltage) input through the comprehensive component monitor (CCM). If during key ON engine OFF or key ON engine running the air flow (or voltage) changes above a maximum calibrated limit, the test fails.
MAF sensor screen is blocked
MAF circuit shorted to VPWR
Damaged MAF sensor
Damaged PCM
A MAF V PID (MAF PID) reading less than 4.6 volts in continuous memory or key ON and engine running indicates a hard fault.
Sample testing procedure here: http://easyautodiagnostics.com/ford_maf/maf_sensor_ford_1.php
DTC code details:
P0103 - Mass Air Flow (MAF) Circuit High Input
The MAF sensor circuit is monitored by the PCM for high air flow (or voltage) input through the comprehensive component monitor (CCM). If during key ON engine OFF or key ON engine running the air flow (or voltage) changes above a maximum calibrated limit, the test fails.
MAF sensor screen is blocked
MAF circuit shorted to VPWR
Damaged MAF sensor
Damaged PCM
A MAF V PID (MAF PID) reading less than 4.6 volts in continuous memory or key ON and engine running indicates a hard fault.
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26 Posts
Battery has now drained, don't yet know why. Having battery recharged and will check alternator output. If Alt. is good it should keep running if disconnected from battery, right?
I will re-clean and check all wiring in to MAF. But why would my battery drain?
You mentioned a a MAF short to VPWR, is that only in that circuit or will it drain my battery?
I will re-clean and check all wiring in to MAF. But why would my battery drain?
You mentioned a a MAF short to VPWR, is that only in that circuit or will it drain my battery?
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You might want to go to the parts store and get some cleaner for the Maf sensor , I've heard that the carb cleaner and throttle body cleaner leaves a small amount of film on the Maf .
Also you are gonna need to plug that hole , more than likely its sucking in to much air for the computer to adjust for .
Also you are gonna need to plug that hole , more than likely its sucking in to much air for the computer to adjust for .
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Disconnected any battery lead while the engine is running is a bad idea. You can cause large voltage spikes that can damage the sensitive electronics on modern cars.
A quick way to test the alternator output is to measure the voltage at the battery with the car running with a multimeter; it should be approx. 14 - 14.5V. With the engine off, voltage should be around 12V - 12.5V.
It is possible to have two unrelated problems on the car (bad MAF and bad alt) or two related problems (bad alt output indirectly causing bad sensor readings) or it could be something else (bad battery which alt can't charge giving poor system voltage.)
I'd start simple: check that your battery is in good condition and can maintain a consistent charge. That usually involves having it load tested.
Since the resonator is before the MAF, it's likely not an issue. However since it's easy to replace, replace it until you get the problem sorted out.
Also, as was mentioned, use the proper cleaner for engine sensor components.
A quick way to test the alternator output is to measure the voltage at the battery with the car running with a multimeter; it should be approx. 14 - 14.5V. With the engine off, voltage should be around 12V - 12.5V.
It is possible to have two unrelated problems on the car (bad MAF and bad alt) or two related problems (bad alt output indirectly causing bad sensor readings) or it could be something else (bad battery which alt can't charge giving poor system voltage.)
I'd start simple: check that your battery is in good condition and can maintain a consistent charge. That usually involves having it load tested.
Since the resonator is before the MAF, it's likely not an issue. However since it's easy to replace, replace it until you get the problem sorted out.
Also, as was mentioned, use the proper cleaner for engine sensor components.
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I had the battery recharged, said it is good. Car started right up. Checked voltage at battery terminals was 12.08. The only code I am getting is the MAF still. The alternator is computer controlled right? and the battery only charges when it calls for it? And it should throw a code for that? I am stumped here. I ordered a new alternator and am in need of diagrams to do the replace.
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If the voltage was measured with the car running, 12.08V is low.
The voltage regulator within the alternator itself determines the voltage output of the alternator. The alternator must consistently put out a voltage greater than that of the battery under all conditions in order to keep the battery charged. The amount of voltage the alternator puts out varies depending on electrical load but it's typically 13.0 - 14.5V.
Depending on the type of problem, the PCM may log a DTC code. More typically, the battery light on the dash will light, intermittently at first and then permanently.
Before you replace the alt, you should eliminate the simple less costly causes: poor electrical connections, broken or chafed wires, possible shorts or corroded batter terminal connections. On some models, there is also a large fusible link within the thick red alternator to battery cable.
Purely guessing, I'd suggest this: Your alternator may be fine (no dash light) but you may have blown a fuse or have a loose cable somewhere (no appreciable alt voltage output). The MAF sensor may be the source of a dead short.
Did all your problem start when your MAF code came up? If so, fix the obvious first then re-assess and proceed with the next steps.
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Problem started with a bad coil. Replaced that and the plugs. Drove through a bunch of rain last week and then drove to Houston 300 miles, then back to Corpus. Then the battery weakened, then died. I am buy a charger and am going to recheck all the connections and measure voltage out of the alternator. If I can reach the wire. I will eliminate the obvious. The MAF started 2 weeks ago after I took off the resonator box. I cleaned the MAF at that time too with carb cleaner, but it was driving like a bat out of hell. Altho I think it was running rich, mpg has been poor.
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