Who's the MAP sensor expert?
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Rookie
Joined: Jan 2006
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From: Connecticut
Who's the MAP sensor expert?
Hi Guys,
I have a problem with my 2001 Ram. It's "bucking" somewhere around 1800-2000 rpm, or when I'm just about to, or have just upshifted.
I have 2 codes locked in. The first is P0123 for the throttle position sensor. The second is code P0121 for the MAP sensor. The manual says that "coded" sensor may be afffected by another part that is actually the bad part, so the position sensor may not be the actual bad part. Moving on....
I've checked the throttle position sensor out of circuit with an ohmmeter both across the terminals (5.06Kohms), and ramping up and down ~500.0 to 5.2Kohms). The input voltage is 5.22 volts when probed in circuit. I compared these readings with the manual and a new sensor and they appear very close. Installed a new throttle position sensor and still have the same symptoms.
The manual does well for telling me how the MAP sensor senses, but isn't great for how to troubleshoot.
Again, I have 5.20 vdc supplied to the sensor. From the wire side left to right, I've got 5.2 vdc, 4.7 vdc and ground, in circuit and at idle. Out of circuit I have 43Kohms from left to center, and right to center. With a very small vacuum applied, the resistance does not change out of circuit. Re-installed MAP sensor and connected.
When gradual pedal is applied from idle, the engine RPM gradually increases until ~1800 RPM, hesitates, then surges up to about 2500 RPM.
The codes say the two sensors must correlate with engine RPM, and must agree with what is going on. Maybe when the hesitation or the surge occurs is when the code locks in.
I need to probe all of your experiences with this unit. The part is expensive, so I'd like a little more confirmation that the MAP sensor could be bad.
So what do you think?
Thanks,
Steve
I have a problem with my 2001 Ram. It's "bucking" somewhere around 1800-2000 rpm, or when I'm just about to, or have just upshifted.
I have 2 codes locked in. The first is P0123 for the throttle position sensor. The second is code P0121 for the MAP sensor. The manual says that "coded" sensor may be afffected by another part that is actually the bad part, so the position sensor may not be the actual bad part. Moving on....
I've checked the throttle position sensor out of circuit with an ohmmeter both across the terminals (5.06Kohms), and ramping up and down ~500.0 to 5.2Kohms). The input voltage is 5.22 volts when probed in circuit. I compared these readings with the manual and a new sensor and they appear very close. Installed a new throttle position sensor and still have the same symptoms.
The manual does well for telling me how the MAP sensor senses, but isn't great for how to troubleshoot.
Again, I have 5.20 vdc supplied to the sensor. From the wire side left to right, I've got 5.2 vdc, 4.7 vdc and ground, in circuit and at idle. Out of circuit I have 43Kohms from left to center, and right to center. With a very small vacuum applied, the resistance does not change out of circuit. Re-installed MAP sensor and connected.
When gradual pedal is applied from idle, the engine RPM gradually increases until ~1800 RPM, hesitates, then surges up to about 2500 RPM.
The codes say the two sensors must correlate with engine RPM, and must agree with what is going on. Maybe when the hesitation or the surge occurs is when the code locks in.
I need to probe all of your experiences with this unit. The part is expensive, so I'd like a little more confirmation that the MAP sensor could be bad.
So what do you think?
Thanks,
Steve
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Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Who's the MAP sensor expert?
You are more likely to have a TPS problem.
It is also possible that a solenoid inside your auto trans is beginning to fail, which has been a common problem.
Check out Dave Fritz's valuable list of TSB's
http://dodgeram.info/tsb/index.html
Below is an old post that might help with determining if your MAP is normal:
----
On a trip from Durham NC to Knoxville TN on Saturday 5-13-00
I decided to take a side trip up Mount Mitchell,
the highest mountain east of the Mississippi (6824 ft).
My truck is a 1995 club cab 2wd with the 5.9V8.
Here's what I found on the MAP sensor readings:
The Ram was cold and had sat overnight in Durham when I hooked up the ScanTool
and did a key-on but engine off MAP reading: 29.4 inches Hg/ 4.53 volts. My
cheap pocket hiker's altimeter also said that the reading should be 29.4.
Battery temp sensor read 73F.
With engine on, at idle the MAP read 11.7 inches Hg/1.55 volts.
I drove 10 miles to a gas station and filled up with Amoco 87 octane.
The coolant temp had come up to the 195 degree level.
With the key-on but engine-off at the gas station the MAP was still 29.4/4.53
volts. I was glad to see this as I was concerned that maybe underhood
temperature affects the MAP reading. Apparently it does not much.
I did a full throttle entry onto I40 East.
The initial MAP reading was 28.1 inches Hg but began to drop to about 27.9 as
the rpms got close to 4500 rpm.
I guess this means that the combination of the Dodge-Dealer-sold KN air
cleaner element in the stock air cleaner hose system, and the fully opened
butterflys of the stock throttle body restricts the airflow at full throttle
by about 1.5 inches of Hg, or about 0.8 psi.
At Morganton NC I stopped again for 87 octane Amoco gas. The pocket altimeter
showed an altitude of 975 feet. The key-on engine-off MAP reading was 28.8/
4.41volts. I checked my mpg and had gone 174.5 miles on 8.08 gallons for 21.6
at a mostly cruise controled 70 mph. That is one of the best mpg I have ever
gotten at 70.
I took the turn-off at Marion NC and drove up the mountain. Ram seemed to
handle the climb fine. Overlook views and the look of the spring trees made me
glad i took this side trip.
At the Mt Mitchell parking lot the sign says 6578 feet. My pocket altimeter
read 6625 feet. The official looking big brass barometer at the ranger
station next to the parking lot read 23.41 inches Hg. The key-on engine off
reading of my Ram's MAP read 23.8/3.57 volts.
On top of the mountain the temperature was now about 50 degrees and the wind
was gusting to 30-40 mph. Clouds would blow in and fog the place in for 3-4
minutes then turn to a slightly hazy clear view.
I reset my pocket altimeter to read 23.41 at 6575 feet and headed down the
mountain.
At an overlook the sign read 5200 elevation and the key-on engine-off MAP
reading was 24.9/3.76 volts. Altimeter read 24.5.
3926 feet overlook sign. MAP 26.2/3.96volts. Altimeter 25.65
3107 feet MAP 26.9/4.08volts Altimeter 26.3
2000 feet/27.5 inches Hg on Pocket Altimeter at road junction at Asheville:
Ram's MAP 27.7/4.24 volts.
What I got out of this side trip was that my MAP sensor seems to read slightly
high: approximately 23.8 divided by 23.41 times 100% = 1.7%
I would guess that this means that the computer sets the mixture 1.7% rich at
full throttle.
For what it is worth, with this MAP sensor my Ram will ping slightly (sounds
like one cylinder) from 3800-4200 rpm at full throttle on 87 octane gas. To
hear the ping I need to roll the windows up and turn off the radio. On 89
octane gas the ping almost completely goes away, and with 93 octane there is
no hearable ping. I presently have a 205 Stant 'standard grade' thermostat
installed but the coolant temp on the ScanTool almost always reads 195F, so I
guess the thermostat wasn't made right. I also have Bosch Platinum+4
sparkplugs and they do seem to ping a bit more than old style single Bosch
Platinum sparkplugs FR7DPX.
I hope these reading may help someone else investigating their Ram's MAP
sensor.
It is also possible that a solenoid inside your auto trans is beginning to fail, which has been a common problem.
Check out Dave Fritz's valuable list of TSB's
http://dodgeram.info/tsb/index.html
Below is an old post that might help with determining if your MAP is normal:
----
On a trip from Durham NC to Knoxville TN on Saturday 5-13-00
I decided to take a side trip up Mount Mitchell,
the highest mountain east of the Mississippi (6824 ft).
My truck is a 1995 club cab 2wd with the 5.9V8.
Here's what I found on the MAP sensor readings:
The Ram was cold and had sat overnight in Durham when I hooked up the ScanTool
and did a key-on but engine off MAP reading: 29.4 inches Hg/ 4.53 volts. My
cheap pocket hiker's altimeter also said that the reading should be 29.4.
Battery temp sensor read 73F.
With engine on, at idle the MAP read 11.7 inches Hg/1.55 volts.
I drove 10 miles to a gas station and filled up with Amoco 87 octane.
The coolant temp had come up to the 195 degree level.
With the key-on but engine-off at the gas station the MAP was still 29.4/4.53
volts. I was glad to see this as I was concerned that maybe underhood
temperature affects the MAP reading. Apparently it does not much.
I did a full throttle entry onto I40 East.
The initial MAP reading was 28.1 inches Hg but began to drop to about 27.9 as
the rpms got close to 4500 rpm.
I guess this means that the combination of the Dodge-Dealer-sold KN air
cleaner element in the stock air cleaner hose system, and the fully opened
butterflys of the stock throttle body restricts the airflow at full throttle
by about 1.5 inches of Hg, or about 0.8 psi.
At Morganton NC I stopped again for 87 octane Amoco gas. The pocket altimeter
showed an altitude of 975 feet. The key-on engine-off MAP reading was 28.8/
4.41volts. I checked my mpg and had gone 174.5 miles on 8.08 gallons for 21.6
at a mostly cruise controled 70 mph. That is one of the best mpg I have ever
gotten at 70.
I took the turn-off at Marion NC and drove up the mountain. Ram seemed to
handle the climb fine. Overlook views and the look of the spring trees made me
glad i took this side trip.
At the Mt Mitchell parking lot the sign says 6578 feet. My pocket altimeter
read 6625 feet. The official looking big brass barometer at the ranger
station next to the parking lot read 23.41 inches Hg. The key-on engine off
reading of my Ram's MAP read 23.8/3.57 volts.
On top of the mountain the temperature was now about 50 degrees and the wind
was gusting to 30-40 mph. Clouds would blow in and fog the place in for 3-4
minutes then turn to a slightly hazy clear view.
I reset my pocket altimeter to read 23.41 at 6575 feet and headed down the
mountain.
At an overlook the sign read 5200 elevation and the key-on engine-off MAP
reading was 24.9/3.76 volts. Altimeter read 24.5.
3926 feet overlook sign. MAP 26.2/3.96volts. Altimeter 25.65
3107 feet MAP 26.9/4.08volts Altimeter 26.3
2000 feet/27.5 inches Hg on Pocket Altimeter at road junction at Asheville:
Ram's MAP 27.7/4.24 volts.
What I got out of this side trip was that my MAP sensor seems to read slightly
high: approximately 23.8 divided by 23.41 times 100% = 1.7%
I would guess that this means that the computer sets the mixture 1.7% rich at
full throttle.
For what it is worth, with this MAP sensor my Ram will ping slightly (sounds
like one cylinder) from 3800-4200 rpm at full throttle on 87 octane gas. To
hear the ping I need to roll the windows up and turn off the radio. On 89
octane gas the ping almost completely goes away, and with 93 octane there is
no hearable ping. I presently have a 205 Stant 'standard grade' thermostat
installed but the coolant temp on the ScanTool almost always reads 195F, so I
guess the thermostat wasn't made right. I also have Bosch Platinum+4
sparkplugs and they do seem to ping a bit more than old style single Bosch
Platinum sparkplugs FR7DPX.
I hope these reading may help someone else investigating their Ram's MAP
sensor.
Thread Starter
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Rookie
Joined: Jan 2006
Posts: 53
Likes: 0
From: Connecticut
RE: Who's the MAP sensor expert?
Thanks for your reply.
I don't suspect it's a TPS problem, as I get the same ohmic and voltage readings on both the original and new replacement TPS units.
About a month ago, I replaced the air filter. About a week ago, after the code P0123 came in, I replaced the OE Champion plugs (overgapped by ~.014") with Bosch Platinum 4 plugs. Shortly after that the code P)121 came in.
The attachment you sent is very interesting. These sensors are VERY sensitive, and can affect the fuel/air mix greatly.
Due to an appaling lack of information and T/S tools on my part, I'm thinking of installing a MAP sensor this afternoon. In our area, labor costs are ~$85.00/hr, and the retail cost for the MAP sensor is ~$165.00. If I install it myself for ~$97.00 Autozone price, even if I have to take it to the dealer afterward (who might likely change it out anyway) I might just come out ahead in the long run.
What do you think?
Steve
I don't suspect it's a TPS problem, as I get the same ohmic and voltage readings on both the original and new replacement TPS units.
About a month ago, I replaced the air filter. About a week ago, after the code P0123 came in, I replaced the OE Champion plugs (overgapped by ~.014") with Bosch Platinum 4 plugs. Shortly after that the code P)121 came in.
The attachment you sent is very interesting. These sensors are VERY sensitive, and can affect the fuel/air mix greatly.
Due to an appaling lack of information and T/S tools on my part, I'm thinking of installing a MAP sensor this afternoon. In our area, labor costs are ~$85.00/hr, and the retail cost for the MAP sensor is ~$165.00. If I install it myself for ~$97.00 Autozone price, even if I have to take it to the dealer afterward (who might likely change it out anyway) I might just come out ahead in the long run.
What do you think?
Steve
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Who's the MAP sensor expert?
When the TPS sensor goes bad it is usually only in one spot of its range of motion.
There is nothing wrong with trying a MAP sensor out to see if it corrects the problem.
It is also worth reading over these particular TSB's:
http://dodgeram.info/tsb/2000/21-04-00.htm
http://dodgeram.info/tsb/1998/18-48-98.htm
There is nothing wrong with trying a MAP sensor out to see if it corrects the problem.
It is also worth reading over these particular TSB's:
http://dodgeram.info/tsb/2000/21-04-00.htm
http://dodgeram.info/tsb/1998/18-48-98.htm
Thread Starter
|
Rookie
Joined: Jan 2006
Posts: 53
Likes: 0
From: Connecticut
RE: Who's the MAP sensor expert?
I think I found the problem based upon another viewer's experience:
From SST_Ram
"I had a neighbor who had a similar problem. I scanned his PCM, and also got a high voltage at TPS error. The thing is, this only occured when he put on his A/C. After some research and checking wiring diagrams, the three wires coming from the TPS go directly to the PCM. No other grounds or interconnections exsist. The problem was the PCM. What happened was, the PCM supplies the 5 volts to the TPS, when my neighbor turned on his A/C, I got 12 volts at the TPS. The PCM somehow shorted internally everytime he turned his A/C on. He replaced the PCM, and had to get it re-flashed at the dealship. No problems since......I hope this helps.....
I recently replaced both the TPS and the MAP sensor, even though they metered out well in a static test. I still saw the problems at RPM. Meter checks between the PCM and the sensors looked good.
I pulled the A/C clutch relay in the Power Distribution Center (PDC). All ran well. Replaced the relay in the PDC and disconnected the connector near the fuel rail that goes to the A/C clutch. All went well.
It seemed that anytime the A/C clutch is allowed to engage, the problem shows up. Disconnect anything in between the power and the A/C clutch and the problem goes away.
It looks like SST_Ram has the correct solution for my problem. I've been searching in this forum for an answer for over a week. I've never used the search combination I've just used, and now it seems I found the answer.
Thanks for your work and your research. I'll try to let you know how I made out.
Who has PCM's for the best price?
Steve
From SST_Ram
"I had a neighbor who had a similar problem. I scanned his PCM, and also got a high voltage at TPS error. The thing is, this only occured when he put on his A/C. After some research and checking wiring diagrams, the three wires coming from the TPS go directly to the PCM. No other grounds or interconnections exsist. The problem was the PCM. What happened was, the PCM supplies the 5 volts to the TPS, when my neighbor turned on his A/C, I got 12 volts at the TPS. The PCM somehow shorted internally everytime he turned his A/C on. He replaced the PCM, and had to get it re-flashed at the dealship. No problems since......I hope this helps.....
I recently replaced both the TPS and the MAP sensor, even though they metered out well in a static test. I still saw the problems at RPM. Meter checks between the PCM and the sensors looked good.
I pulled the A/C clutch relay in the Power Distribution Center (PDC). All ran well. Replaced the relay in the PDC and disconnected the connector near the fuel rail that goes to the A/C clutch. All went well.
It seemed that anytime the A/C clutch is allowed to engage, the problem shows up. Disconnect anything in between the power and the A/C clutch and the problem goes away.
It looks like SST_Ram has the correct solution for my problem. I've been searching in this forum for an answer for over a week. I've never used the search combination I've just used, and now it seems I found the answer.
Thanks for your work and your research. I'll try to let you know how I made out.
Who has PCM's for the best price?
Steve
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Who's the MAP sensor expert?
That is impressive diagnostic work!
And the search function when used with the right keywords is incredibly powerful.
Perhaps it is possible that your AC clutch has shorted turns in the coil
and is pulling excessive current
that even a 'good' PCM switching can't handle
without excessive voltage drop?
You might be able to diagnose that by checking the ohms of resistance of a 'known good' AC clutch against your clutch's measurements.
Here's some discount Dodge parts places from an earlier post:
---
in no particular order:
http://www.chryslerpartsdirect.com/
http://dodge-auto-parts-dealer.com/
https://www.dodgeparts.com/oe_parts_catalog.html
http://www.worldparts.com/tenaflychrysler/
http://www.worldparts.com/kollerdodge/
http://chrysler.darcars.com/parts_center.htm?bhjs=0
http://moparts.com/
www.makeitmopar.com
http://www.mopar4less.com/accessories.html
http://www.rockauto.com/
http://chucker54.stores.yahoo.net/
(above is Mancini Racing)
at this Hendrick Dodge parts webpage
call the 800-407-3725 number,
tell them the parts,
then add you are comparing prices on the internet
and "what's your best price?"
http://www.hendrickdodge.com/partsse...orderparts.jsp
here's another long list of online Dodge part sellers:
http://www.parts.com/index.cfm?actio...ubCategoryID=8
--
to search the salvage yards
two weblinks are
http://www.junkyarddog.com/
http://www.car-part.com/
And the search function when used with the right keywords is incredibly powerful.
Perhaps it is possible that your AC clutch has shorted turns in the coil
and is pulling excessive current
that even a 'good' PCM switching can't handle
without excessive voltage drop?
You might be able to diagnose that by checking the ohms of resistance of a 'known good' AC clutch against your clutch's measurements.
Here's some discount Dodge parts places from an earlier post:
---
in no particular order:
http://www.chryslerpartsdirect.com/
http://dodge-auto-parts-dealer.com/
https://www.dodgeparts.com/oe_parts_catalog.html
http://www.worldparts.com/tenaflychrysler/
http://www.worldparts.com/kollerdodge/
http://chrysler.darcars.com/parts_center.htm?bhjs=0
http://moparts.com/
www.makeitmopar.com
http://www.mopar4less.com/accessories.html
http://www.rockauto.com/
http://chucker54.stores.yahoo.net/
(above is Mancini Racing)
at this Hendrick Dodge parts webpage
call the 800-407-3725 number,
tell them the parts,
then add you are comparing prices on the internet
and "what's your best price?"
http://www.hendrickdodge.com/partsse...orderparts.jsp
here's another long list of online Dodge part sellers:
http://www.parts.com/index.cfm?actio...ubCategoryID=8
--
to search the salvage yards
two weblinks are
http://www.junkyarddog.com/
http://www.car-part.com/
Thread Starter
|
Rookie
Joined: Jan 2006
Posts: 53
Likes: 0
From: Connecticut
RE: Who's the MAP sensor expert?
That is an impressive list of parts suppliers!
I have an appointment for a dealer visit of Friday. If it is indeed the PCM module, it is covered by the mfg. 8 year/80,000 mile warranty. I'll let all of you know how it goes.
Steve
I have an appointment for a dealer visit of Friday. If it is indeed the PCM module, it is covered by the mfg. 8 year/80,000 mile warranty. I'll let all of you know how it goes.
Steve
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Joined: Jul 2006
Posts: 1
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RE: Who's the MAP sensor expert?
My only experience with a MAP sensor was a 1991 Caravan. The car would start and run for 1 or 2 seconds before stalling. There were no engine codes recorded. ALLPAR.com said to remove the sensor and the car would run, although it would not run smoothly. Removed the sensor and it ran rough; replaced the sensor and it started and continued running smooth.
