Failed MAP cause low power?

[skyhigh4by]

Can a failed or failing MAP sensor cause my truck to be very sluggish down low and continuously the P0234 code? 

 

I once upon a time had an edge ez but it’s gone now. The boost elbow that came with it is still installed though. I have a fass lift pump and a FP gauge. Otherwise all stock. Truck feels like a total pig off the line and doesn’t feel like it starts making any power until 1800 rpm or so. Also has trouble holding highway speed in OD on any hills even empty. 

[Me78569]

Our trucks are fueled based on map input.  A failed map will result in nearly no fuel.

[skyhigh4by]

3 minutes ago, Me78569 said:

Our trucks are fueled based on map input.  A failed map will result in nearly no fuel.

Okay I’m somewhat happy to hear that. Is there a way I can definitively condemn the MAP or should I just go ahead and replace it? 

[Me78569]

have you looked at the troubleshooting article for that code?  

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/

 

 

 

 

[skyhigh4by]

9 minutes ago, Me78569 said:

have you looked at the troubleshooting article for that code?  

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/

 

 

 

 

Yes I have. Maybe I’m interpreting it wrong but I don’t get how that proves whether the MAP is good or not. Even with a stuck wastegate and totally stock fueling shouldn’t it not exceed boost limits? That article says to replace the wastegate and mentions nothing of the MAP sensor itself needing replacement. Is it just a part that never fails and if it had codes it’s pointing towards other parts being the cause? 

[dripley]

You also should remove the boost elbow or close it all the way. Anything over 20 or so psi will set the the 234 code.My MAP sensor crapped the bed not long ago with the same symptoms. Had to make big runs at the hills just o get over them. The MAP is a $100 to $200 sensor so some trouble shooting would not hurt. The only place that had it in mine was Oriellys and they just happened to be the cheapest at about $105. 

3 minutes ago, skyhigh4by said:

Yes I have. Maybe I’m interpreting it wrong but I don’t get how that proves whether the MAP is good or not. Even with a stuck wastegate and totally stock fueling shouldn’t it not exceed boost limits? That article says to replace the wastegate and mentions nothing of the MAP sensor itself needing replacement. Is it just a part that never fails and if it had codes it’s pointing towards other parts being the cause? 

You will exceed boost pressures with a stuck waste gate. Thats why the waste gate is there. It opens near 20 psi if it is the stock one. But if it is stuck closed you will exceed the 20 or 22 psi to throw the code. I take you do not have a boost gauge.

[Me78569]

very true.  

 

follow the multimeter troubleshooting in the article it will tell you if the map is reading 0 psi at idle or if it is reading max at idle setting the p0234. 

 

unless you are driving WOT all the time then I would not expect an overboost code all the time just because of the elbow though.

[skyhigh4by]

I don’t have a boost gauge. It’s one of many many things on the to do list. I very rarely go beyond 3/4 throttle. The low power problem feels like it’s a somewhat recent thing I don’t remember it being so gutless and it almost feels as if it’s slowly getting worse. The VP has maybe 20k miles. Truck has under 120k miles. 

 

I guess i will will try to see if the wastegate is stuck. The boost elbow isn’t adjustable and I don’t think I have the stock piece around. 

Edited May 16, 2019 by skyhigh4by

[Me78569]

Probe the map sensor output wire, pin c of the sensor, using a multimeter at Idle state.  The Sensor should be outputting near 4.5v.  anything more than .25 less than that means your map sensor is reading boost at idle.  If it reads .5v at idle then you will trip a code p0237, but if it reads ~4v-1v at idle then you will get this p0234 code.  

 

effectively means the map sensor is stuck reading a single psi reading and not functioning.

Edited May 16, 2019 by Me78569

[dripley]

I have an aftermarket waste gate actuator, Banks Big head, It opens near 33 psi. When the Banks tuner crapped out I drove it for 3 years before getting the comp. Towing or not I had to drive it by the boost gauge to keep from setting the code or the engine defueling. I also had RV 275's which will push the boost up more.

5 minutes ago, skyhigh4by said:

I don’t have a boost gauge. It’s one of many many things on the to do list. I very rarely go beyond 3/4 throttle. The low power problem feels like it’s a somewhat recent thing I don’t remember it being so gutless and it almost feels as if it’s slowly getting worse. The VP has maybe 20k miles. Truck has under 120k miles. 

 

I guess i will will try to see if the wastegate is stuck. The boost elbow isn’t adjustable and I don’t think I have the stock piece around. 

When my map was failing I had a scan gauge II hooked up and when the problem would occur, just like what you are experiencing, the SCII would see 14.6 psi on the MAP and never move. I did get to hook it up to a Snap on Versus and read 0. that is how I determined mine was bad. Mine was doing the same as yours, just pain gutless.

 

 

[skyhigh4by]

Okay thanks. I have a scan gauge I could hook up and an OTC genesys I can watch live data with so I’ll check into that. 

[Mopar1973Man]

Scan Gauge II and others will misreport the MAP sensor. Being Cummins uses a special kind of math to report boost correctly. 

 

 

 

 

 

[dripley]

I agree. Mine read whacky numbers for boost. The 14.6 reading was the SG version of zero. The Snap on read 0. Neither of them moved while driving. A new sensor did fix my issues. 

 

To the OP, whule sensor did fix mine it still could be wiring issue. I rolled the dice and won.

[Me78569]

you dont need to see exact numbers, what you are looking for is it reads something steady at idle, then it increases with load to a poin that makes sense.

[dripley]

2 hours ago, Me78569 said:

you dont need to see exact numbers, what you are looking for is it reads something steady at idle, then it increases with load to a poin that makes sense.

My SGII would do that when the sensor was working but at wierd numbers. I idled around 27 psi and WOT around 34 psi. But it did rise and fall like it should until the sensor failed.

[skyhigh4by]

I finally got a chance to put a voltmeter on the map sensor. I got 0.49v from pin c at idle. I’ve never noticed a p0237 code before when I’ve scanned only ever seen p0234??

[dripley]

Did you drive the truck while connected to the sensor? If not you need to to see if voltage changes. If stays constant the sensor is most likely dead. It could still be a bad wire, thats where code diagnostics come in.

 

While I did encounter the 237 code during my problem it only showed up occasionally. 

[skyhigh4by]

No I didn’t drive. I just had a paperclip probe stuck in the plug and touched it will the voltmeter. I will have to make up something to tap in more permanently to drive and monitor. 

 

Or or could I not just use a scan tool to see map output voltage or is that not accurate? 

 

Also so I just finally got around to testing for boost leaks and I found leaks at every clamp. With my compressor going I couldnt even seem to build more than a few psi it all just leaked out. It doesn’t really make sense to me that was going on and I was still getting an overboost code? I am just going through all the connections now to stop the leaks  

Edited May 30, 2019 by skyhigh4by

[dripley]

You might be surprised at how much boost you can build even with boost leaks. Take one of the couplings off one day and feel how air the turbo will move at idle. I was surprised. The flow from that will oustrip what I can put in it with my small pancake compressor. The turbo produces a whole lot more volume.

 

Your scanner might read it, but I dont know what have. It does not have to display volts either. It can display psi. You need to see it move when you stick your foot in it. Mine did not move even though I could build about 4 or 5 psi. As mentioned earlier if the ECM does not see any boost it is not going to fuel the engine as it should, hence the weak running truck.

[Me78569]

.4 v at idle is way to low.  it should be near 4.5v at idle.

 

Your map sensor is hosed if your truck is giving 4.5v to the sensor.