Testing MAP sensor, intermittant code P2036, wird result. - Diesel Forum

mikeceli · 05-30-2009, 01:00 PM

Hi Folks!

On our 2000 Excursion 4x4 7.3, I have turned up an intermittant Code P0236, for about a year. The SES light lately resets itself (off) and I have, in the past, cleared the code w/ my Actron 9145/9190 Scanner.

TEST RESULT: When I view datastream, at idle, MAP shows 21 " HG.

Engine off MAP 0

when I "T" in 10 PSI air pressure, to the MAP sensor and a auxilery boost guage, Actron reads MAP 59 " HG.

What gives? It seem my Actron is confused, reading vacuum (inches mercury, w/ 10 PSI). I haven't road tested the vehicle w/ the Actron and boost gauge hooked up, YET.

Vehicle runs fine.

Thanks.

CORRECTED CODE ON EDIT to P0236

calico5string · 05-30-2009, 04:09 PM

I think you mean a code P0236 (not 2036).

Sounds/looks like a bad MAP sensor.

There are a number of diagnostic tests you could perform to troubleshoot the problem, the simplest of which is to make sure you have no leaks in the MAP pressure line(s). Other tests involve checking the output voltage of the sensor at a fixed pressure (10 psig input should give 2.8v output/+-0.3v). You could also have an intermitent short or open in the MAP wiring between the sensor and the PCM.

...or you could just replace the MAP sensor, clear the code and see what happens.

With a bad MAP signal, the PCM will default to "assumed" values, and the truck will seem to run ok.

I can post up a picture of the MAP sensor and circuit, if needed.

Good luck...

**klhansen** · 05-30-2009, 06:36 PM

I'll have to agree that it sounds like your MAP sensor output is biased for some reason.

FYI, inches of Hg isn't necessarily a vacuum measurement, it can go positive as well. It's just a different unit of pressure, commonly used for vacuum because it's a "finer" scale than psi.

"TEST RESULT: When I view datastream, at idle, MAP shows 21 " HG."
I suspect your scan tool is reading MAP (Manifold Absolute Pressure), but it's a bit low. At idle, MAP should be 14.7 psi +/- or about 29.9" Hg.

"Engine off MAP 0" would be correct if your scale is in "gauge" pressure. If in absolute pressure, it should read around 29" Hg or one atmosphere. The best way to check that is compare MGP (manifold gauge pressure) with EBP and BARO sensors. They should read within 1 psi (or 2" Hg) of each other with the engine off.

10 psi gauge should equal 20" Hg gauge or 50"Hg absolute pressure (adding 14.7 psi for atmospheric pressure). So if your 59"Hg is absolute, your MAP sensor is reporting about 15 psig versus your gauge reading of 10 psi. Maybe your gauge isn't properly calibrated, but 5 psi is a long ways off.

mikeceli · 05-31-2009, 01:41 AM

Thank you both for the info!

I would like to run an output voltage test, on the MAP, before I replace it.

I have the Ford shop manuals vol 1 &2 , but no emmission/diagnostic manual.

At which of the 2 or 3 wires, on the MAP, should I measure output voltage(at 10PSIG)?

Thanks, Mike

calico5string · 05-31-2009, 01:02 PM

Quote:

Originally Posted by mikeceli

Thank you both for the info!

I would like to run an output voltage test, on the MAP, before I replace it.

I have the Ford shop manuals vol 1 &2 , but no emmission/diagnostic manual.

At which of the 2 or 3 wires, on the MAP, should I measure output voltage(at 10PSIG)?

Thanks, Mike

Test MAP output between "MAP SIGNAL" and "SIG RTN".

You might also verify the +5v reference voltage between "V-REF" and "SIG RTN".

The Ford "Powertrain Control/Emissions Diagnosis" Manual has been an invaluable reference for me.

Here ya go:

mikeceli · 06-01-2009, 08:33 AM

Thanks you all very much! I WILL advise outcome, when I make tests/repair. I worked 12 last night and have 2 more nights, this week. It might be Thursday.

mikeceli · 06-02-2009, 06:29 PM

Confirming I take my voltage readings between "V-REF and SIG RETERN", not to ground?.

Should be per posted V value chart?

calico5string · 06-03-2009, 12:09 PM

Quote:

Originally Posted by mikeceli

Confirming I take my voltage readings between "V-REF and SIG RETERN", not to ground?.

Should be per posted V value chart?

NO!

Take your readings between "MAP SIGNAL" and Ground (or SIG RTN)

"V-REF" is the +5v input signal. "SIG RTN" is basically the ground (the -5v side) and "MAP SIGNAL" is the MAP sensor output.

mikeceli · 06-05-2009, 12:22 AM

UPDATE UPDATE

Yesterday I obtained the following voltage readings. engine off. metered air pressure "T" ed into MAP, PSI read w/ a auxilery boost gauge

3.9 volt at 11.5 psig should be 1.1 volt
4.4 volt at 14.7 psig " " 1.5 V
4.9 volt at 20 psig " " 2.2 V

referance voltage was correct at 5 volts

So the MAP sensor tests BAD.

NEW development....while driving 70 MPH, engine "hickuped" several times (instantanously lost power for a half second, several times). I then read codes an got a P0344 cam position sensor (problem).

Today I had Ford dealer replace the CPS (free under recall) and I installed a new Ford MAP sensor and cleared the codes.

I will test voltage w/ new MAP sensor and road test. After a few days, I'll report back.

calico5string · 06-05-2009, 12:51 PM

Quote:

Originally Posted by mikeceli

UPDATE UPDATE

Yesterday I obtained the following voltage readings. engine off. metered air pressure "T" ed into MAP, PSI read w/ a auxilery boost gauge

3.9 volt at 11.5 psig should be 1.1 volt
4.4 volt at 14.7 psig " " 1.5 V
4.9 volt at 20 psig " " 2.2 V

referance voltage was correct at 5 volts

So the MAP sensor tests BAD.

NEW development....while driving 70 MPH, engine "hickuped" several times (instantanously lost power for a half second, several times). I then read codes an got a P0344 cam position sensor (problem).

Today I had Ford dealer replace the CPS (free under recall) and I installed a new Ford MAP sensor and cleared the codes.

I will test voltage w/ new MAP sensor and road test. After a few days, I'll report back.

Yep, those numbers would indicate a bad MAPS.

Kind of wierd you suddenly are also getting a CPS code. I would advise you to now carry a spare CPS with you, as there have been many reported problems with the "new" CPS's that Ford is using for the recall. They're pretty easy to change on the road (or side of the road,

).

Thanks a bunch for keeping us all up-to-date with your findings. That's how we all learn!!

mikeceli · 06-05-2009, 01:25 PM

UPDATE UPDATE

I just measured voltage a 0 PSIG and it is now 1.5V, ( was 3.9 v) so w/ the spec of 1.1 v and the tolerance of +- .3 volts, I call that fixed.

Seems to run smoother, on a 2 mile road test. I will advise after a full test drive.

Thanks All!

mikeceli · 06-05-2009, 10:05 PM

UPDATE UPDATE

i HAVE DRIVEN about 20 miles and it is noticably more powerful and smoother, w/ new MAP (and CPS).

The excessive smoke I have noticed, on hard accelaration, for several years!, is gone.
MAP must have been slowly failing, for a while.

calico5string · 06-05-2009, 10:23 PM

Quote:

Originally Posted by mikeceli

UPDATE UPDATE

i HAVE DRIVEN about 20 miles and it is noticably more powerful and smoother, w/ new MAP (and CPS).

The excessive smoke I have noticed, on hard accelaration, for several years!, is gone.
MAP must have been slowly failing, for a while.

Yep, sounds like it.

Glad you got 'er fixed!

2000PSD7.3 · 05-12-2013, 01:17 PM

So, I tested the wrong wire last night....voltage at atmospheric pressure is 1.13. The MAP sensor is good to go. I also scanned the DTC with my SCT tuner and came away with two error codes:
P0237 - Turbo Boost A CKT Low
P0603 - Internal Control Module Keep Alive Memory error.

Any advice...?

Thanks again,
Chris

Dr. Snow · 05-12-2013, 06:06 PM

Chris,

Did you add pressure to bring the map sensor up to a simated full boost? As well as some points in between. This is similar to what I am seeing on my truck. My PCM will not see anything above 13.9 pounds of boost or 3.5 volts from the map sensor. I do have good boost pressure according to my seperate analog gauge though. Order up a gauge and hook it up. Also check foot boost leaked and exhaust leaks at the up pipes and manifolds.