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its related to output speed sensor. the cam sensor would throw a CEL for timing out of sequence code. those other sensors have ZERO to do with tach reading. and even if both were bad would make no difference for the tach.
I am only diagnosing based on what I understand of the situation. He originally replaced the Cam, TPS and MAP sensors (and crank sensor!) because he had codes for them. He replaced them with non OEM sensors. I am just attempting to get him back to OEM spec that way diagnosis can continue to out-rule garbage non-oem parts. However, I will disagree that using improper TPS and MAP sensors can't possibly cause any issue like this. I will however also agree that it is possible that the output sensor is at fault. I am not willing to jump to such a conclusion without verifying the rest of the system is back in spec first. I would then scan the vehicle for any codes including transmission codes if the issues are still happening to see what the computer is saying.
 

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I am only diagnosing based on what I understand of the situation. He originally replaced the Cam, TPS and MAP sensors (and crank sensor!) because he had codes for them. He replaced them with non OEM sensors. I am just attempting to get him back to OEM spec that way diagnosis can continue to out-rule garbage non-oem parts. However, I will disagree that using improper TPS and MAP sensors can't possibly cause any issue like this. I will however also agree that it is possible that the output sensor is at fault. I am not willing to jump to such a conclusion without verifying the rest of the system is back in spec first. I would then scan the vehicle for any codes including transmission codes if the issues are still happening to see what the computer is saying.
I am only diagnosing based on what I understand of the situation. He originally replaced the Cam, TPS and MAP sensors (and crank sensor!) because he had codes for them. He replaced them with non OEM sensors. I am just attempting to get him back to OEM spec that way diagnosis can continue to out-rule garbage non-oem parts. However, I will disagree that using improper TPS and MAP sensors can't possibly cause any issue like this. I will however also agree that it is possible that the output sensor is at fault. I am not willing to jump to such a conclusion without verifying the rest of the system is back in spec first. I would then scan the vehicle for any codes including transmission codes if the issues are still happening to see what the computer is saying.
the tach is driven from the output sensor. I cant say those sensors he replaced are good or not. I did not read all the chatter but I cant tell you the Map sensor might make the car run like **** but would have nothing to do with the tach.

there was an issue that cause a cascade of codes.. related to 5v if i remember correctly a failing cam or crank sensor would cause what they had started with a cluster of codes. correlation is not causation... the problems could have been happening side by side.
 

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the tach is driven from the output sensor. I cant say those sensors he replaced are good or not. I did not read all the chatter but I cant tell you the Map sensor might make the car run like **** but would have nothing to do with the tach.

there was an issue that cause a cascade of codes.. related to 5v if i remember correctly a failing cam or crank sensor would cause what they had started with a cluster of codes. correlation is not causation... the problems could have been happening side by side.
Yet, in his video, the tach is steady, but speedo periodically drops out.

BTW - isn't tach driven by input speed sensor and speedo is driven by output speed sensor?

Who's on first? 🤪
 

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sorry dyslexic moment. tach =spedo
Not a problem. Notice that the OP does say in his first post that the tach periodically drops to zero when the problem is occurring. This is one of those problems that has what appear to be nonsensical symptoms, but that after the cause is found and fixed will make total sense.

One of the difficulties is that the problem is intermittent - got to catch it in the act to measure the failure.

At this point, can't rule out a bad PCM (bad 5 volt bus) or battery (internally shorting - though would expect to see the cluster battery light flickering if that were the case). I hate to introduce more variables without solid solution(s), but could be a bad ground or power connection, loose fuse socket teminal or connector terminal - might be worth removing fuses and de-mating PCM connectors and then reseating.

Might try temporarily disconnecting the headlight switch, as those have been found to cause phantom problems in the past.
 

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Discussion Starter · #27 ·
Not a problem. Notice that the OP does say in his first post that the tach periodically drops to zero when the problem is occurring. This is one of those problems that has what appear to be nonsensical symptoms, but that after the cause is found and fixed will make total sense.

One of the difficulties is that the problem is intermittent - got to catch it in the act to measure the failure.

At this point, can't rule out a bad PCM (bad 5 volt bus) or battery (internally shorting - though would expect to see the cluster battery light flickering if that were the case). I hate to introduce more variables without solid solution(s), but could be a bad ground or power connection, loose fuse socket teminal or connector terminal - might be worth removing fuses and de-mating PCM connectors and then reseating.

Might try temporarily disconnecting the headlight switch, as those have been found to cause phantom problems in the past.
Just saw all the replies. Thanks guys. I got a message today that my cam sensor has arrived. I will go pick it up at lunch today but won't be able to install until tomorrow since I am not driving the car in its current state. One question though, does it not seem odd or point to the possibility of a short in the wiring that this problem didn't exist until I replaced the timing chain and water pump and had the wiring harness disconnected from the sensors and pushed away from the front of the engine? Thanks again. ALSO- I was incorrect in my original post- it was always the speedometer dropping out and never the tach. I just remembered it incorrectly. Sorry for any confusion.
 

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Your question about the coincidence of this starting when you did the work is understandable. For some reason it is not unusual for a timing sensor to start giving problems after timing belt or chain replacement unrelated to wiring issues. It doesn't make sense, but that has always been puzzling.

Sure would be nice if the new OEM sensor fixes it. No use speculating. Fingers crossed!
 

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Discussion Starter · #29 ·
Ok. I put in the brand new dealership cam position and crank position sensors and the original TPS and MAP sensors. So now I'm running with all Mopar sensors. Got in to test drive it, and it's still doing the same thing. Threw a P0068 code 3 miles from the house. Can I cut my 5V wire at the plug by the PCM and route new wire directly to all 4 sensors to see if that solves the problem? That would eliminate any shorting/grounding that might be taking place somewhere in the path of the original 5V wire? Or am I better off to replace all 4 pigtails first to eliminate that as the potential location of the short? Any other ideas?

@peva @PurpleBullet97 @zerokool
 

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Is p0068 the only code? If you're not sure personally I would clear the computer, take it for a drive and see it if it throws more than p0068.
I would also avoid cutting wires unnecessarily without knowing for sure it would solve the issue! I don't think you're there yet personally.

courtesy of Ronbo :

P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION
- HIGH FLOW/VACUUM LEAK

When Monitored and Set Condition:
P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION - HIGH
FLOW/VACUUM LEAK
When Monitored: Engine Running, during all drive modes.
Set Condition: The relationship between the MAP and Throttle exceeds a predetermined
value.

POSSIBLE CAUSES

GOOD TRIP EQUAL TO ZERO
VACUUM LEAK
HIGH RESISTANCE IN MAP (K6) 5 VOLT SUPPLY CIRCUIT
RESISTANCE TO GROUND IN MAP (K6) 5 VOLT SUPPLY CIRCUIT
MAP SENSOR
HIGH RESISTANCE IN (K1) MAP SIGNAL CIRCUIT
RESISTANCE TO GROUND IN (K1) MAP SIGNAL CIRCUIT
HIGH RESISTANCE IN (K4) MAP GROUND CIRCUIT
PCM
TP SENSOR OPERATION
HIGH RESISTANCE IN TP SENSOR (K6) 5 VOLT SUPPLY CIRCUIT
RESISTANCE TO GROUND IN TP SENSOR (K6) 5 VOLT SUPPLY CIRCUIT
TP SENSOR
HIGH RESISTANCE IN (K22) TP SIGNAL CIRCUIT
RESISTANCE TO GROUND IN (K22) TP SENSOR SIGNAL CIRCUIT
HIGH RESISTANCE IN TP (K4) SENSOR GROUND CIRCUIT
PCM

From another forum post investigating a possible vacuum leak same codes:

It is so busy around the master cylinder...I can't see anything. When it is doing it, with the hood up, I can't hear a vaccuum leak. This is the first time I got the loss of power brakes followed by or preceded by the P0121. Kinda happened simultaneously. This morning and last night freezing cold and no symptoms. Is it possible my new TPS is defective? I thought that with the MAP sensor too, when that didn't fix it and traded for another. The TPS was an autozone and much less than the NAPA...maybe NAPA's had better quality? When I first put it in...the check engine went out and after the computer adjusted to it, the idle smoothed out. I thought I fixed it, finally!! Nope. First really cold day and same symptoms with the P0068 code. Symptoms are surging, misfire, feels like going to stall at idle, so you have to brake and gas, at speed you can feel the surge and roughness, but driveable at higher speeds, barely driveable in city driving. Usually doesn't stall though. It seems to always catch itself right before it stalls and surges up.

Just some food for thought. Do you have an electrical issue between your TPS and MAP sensors to the PCM? Are your connectors to those sensors broken or dirty or non conducive for contact? Do you need new a New Mopar MAP sensor? (per the bolded statement...?) New TPS sensor? Maybe your sensors are good and you have a vacuum leak? Maybe Zerokool is right and your transmission has fault codes that you can not see with the key on off method and you have a transmission sensor that's bad?
 

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Discussion Starter · #31 ·
Is p0068 the only code? If you're not sure personally I would clear the computer, take it for a drive and see it if it throws more than p0068.
I would also avoid cutting wires unnecessarily without knowing for sure it would solve the issue! I don't think you're there yet personally.

courtesy of Ronbo :

P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION
- HIGH FLOW/VACUUM LEAK

When Monitored and Set Condition:
P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION - HIGH
FLOW/VACUUM LEAK
When Monitored: Engine Running, during all drive modes.
Set Condition: The relationship between the MAP and Throttle exceeds a predetermined
value.

POSSIBLE CAUSES

GOOD TRIP EQUAL TO ZERO
VACUUM LEAK
HIGH RESISTANCE IN MAP (K6) 5 VOLT SUPPLY CIRCUIT
RESISTANCE TO GROUND IN MAP (K6) 5 VOLT SUPPLY CIRCUIT
MAP SENSOR
HIGH RESISTANCE IN (K1) MAP SIGNAL CIRCUIT
RESISTANCE TO GROUND IN (K1) MAP SIGNAL CIRCUIT
HIGH RESISTANCE IN (K4) MAP GROUND CIRCUIT
PCM
TP SENSOR OPERATION
HIGH RESISTANCE IN TP SENSOR (K6) 5 VOLT SUPPLY CIRCUIT
RESISTANCE TO GROUND IN TP SENSOR (K6) 5 VOLT SUPPLY CIRCUIT
TP SENSOR
HIGH RESISTANCE IN (K22) TP SIGNAL CIRCUIT
RESISTANCE TO GROUND IN (K22) TP SENSOR SIGNAL CIRCUIT
HIGH RESISTANCE IN TP (K4) SENSOR GROUND CIRCUIT
PCM

From another forum post investigating a possible vacuum leak same codes:

It is so busy around the master cylinder...I can't see anything. When it is doing it, with the hood up, I can't hear a vaccuum leak. This is the first time I got the loss of power brakes followed by or preceded by the P0121. Kinda happened simultaneously. This morning and last night freezing cold and no symptoms. Is it possible my new TPS is defective? I thought that with the MAP sensor too, when that didn't fix it and traded for another. The TPS was an autozone and much less than the NAPA...maybe NAPA's had better quality? When I first put it in...the check engine went out and after the computer adjusted to it, the idle smoothed out. I thought I fixed it, finally!! Nope. First really cold day and same symptoms with the P0068 code. Symptoms are surging, misfire, feels like going to stall at idle, so you have to brake and gas, at speed you can feel the surge and roughness, but driveable at higher speeds, barely driveable in city driving. Usually doesn't stall though. It seems to always catch itself right before it stalls and surges up.

Just some food for thought. Do you have an electrical issue between your TPS and MAP sensors to the PCM? Are your connectors to those sensors broken or dirty or non conducive for contact? Do you need new a New Mopar MAP sensor? (per the bolded statement...?) New TPS sensor? Maybe your sensors are good and you have a vacuum leak? Maybe Zerokool is right and your transmission has fault codes that you can not see with the key on off method and you have a transmission sensor that's bad?
It is the only code after this last episode. Originally, this problem started by throwing P0068 and P0121 codes, with the primary code thrown being P0121. I clear them regularly after I do any work to the car. I taped and hose-clamped any vacuum line that looked loose or worn early into this problem just to rule out a vacuum issue. Plus the guy at the shop I took it to said it appeared to be a short to him. He didn't mention a potential vacuum issue. And I would think if it were a vacuum problem with the brake booster/master cylinder I would be able to hear it.
 

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Discussion Starter · #32 ·
Shot a short video of what it's doing this morning. The code thrown was another P0068. It popped up and cleared itself several times on the way in to work this morning. So, after replacing my aftermarket sensors with OEM sensors, I'm right back where I started.
 

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Hopefully you went and got your money back for the aftermarket TPS and MAP sensors!
I would verify wiring that goes to MAP and TPS are good.
I would, because the vehicle is throwing ONLY p0068, check for vacuum leaks again (I personally wouldn't tape hoses I'd replace them)
I would then start suspecting a bad MAP sensor. I would replace only with OEM exact part number for your specific vehicle. Again, the computer is screaming at you for a reason. Whether that reason is valid and you have something wrong electronically (bad wire, bad sensor), or invalid - meaning the vehicles PCM is malfunctioning itself is what you need to figure out!
 

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Discussion Starter · #34 ·
Ok... add this to the "so close yet so far away" file...

At lunch, I drove my car 10 miles to a restaurant. All the way there it was as bad as it's ever been- bucking, hesitating, nearly stalling when I came to a stop, CEL on again and again and again, throwing me out of cruise control everywhere from 65 to 75mph. I was in the restaurant no more than 15 minutes. When I came out, I pulled my original TPS back off and reinstalled the aftermarket one I put on months ago and have been running up until I put the original one back on over the weekend. ALL THE WAY BACK TO WORK there were ZERO problems! No CEL, no bucking, no throwing me out of cruise control, no stalling- none of it! In fact, when I got back to the office, I drove past it just so I could drive around the block to test it in stop-and-go traffic (my bane lately). No issues. When I left the office, I drove it the long way home making a couple of stops along the way. I went more than 35 miles through towns, through stop lights, in and out of stores (I actually stopped to return the crank and cam position sensors to Advance Auto), and again had ZERO issues. It hasn't driven that well since I replaced my water pump and timing chain. Here's where it gets interesting.... I stopped in town, 20 miles away from home and washed my car in the automatic car wash. 9 miles later (about halfway home) my car starts bucking, throwing codes, and kicking me out of cruise as bad as it ever has. Also, it threw a P0121 code again. When I got home, I popped the hood to see if anything under there was wet. I am attaching pictures. The air filter housing was wet and the insulation under the hood was wet. In fact, when I raised the hood up, water ran out of/off of the underside of the hood and fell on the front of the engine. Now, I'm not saying there is a definite relationship between the water and the malfunction, but if you will remember my original post, I have definitely noticed that my problem is worse when it is misty, rainy, foggy, or otherwise wet. The problem has been noticeably better on dry hot days. Is there any way in your minds that water inside the intake tube/housing (prior to the manifold) could be affecting a sensor? TPS? MAP? Or even wiring? Or is this a stunning coincidence? @PurpleBullet97 @peva
Hood Automotive tire Automotive lighting Motor vehicle Automotive design

Motor vehicle Automotive tire Tire Hood Automotive exterior

Motor vehicle Hood Automotive exterior Gas Auto part
 

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Nope, the water isn't doing anything in my opinion... But you are on to something! I wonder what made you put that TPS sensor in! I would personally take this as good news! But! Did the swapping of the sensor eliminate the code P0068? I understand if you didn't disconnect the battery as you were just driving the car and were probably shocked it was running fine. So because we do not know FOR SURE I wouldn't get your hopes up 100% that you've nailed the source of the issue just for this fact alone. (didn't verify P0068 disappeared before 0121 showing back up) I would make the assumption that either the connector that goes to the TPS sensor is failing/failed needs redone/replaced or a new OEM Mopar TPS sensor is needed. (As you have seen, (?) your aftermarket sensor just started working out of the blue for 30 miles before failing again? I would take that back as well!!)
 

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Discussion Starter · #38 ·
Desperation made me put the TPS sensor in. lol. I happened to have it, and I thought "what have I got to lose?" Haha. As far as disconnecting the battery, I always "clear faults" when using my (cheap) code reader to check for what error code I received. So, when I put the TPS sensor in, I cleared the P0068 code. I thought too about the connector being bad since other than the sensor itself, that would be the only other variable I can think of that was affected. Obviously I have run that sensor before, and the car still had problems. However, that was with the old (stock) cam position sensor in it too. I guess deep down inside I was hoping that maybe it was more than one issue contributing to the problems (faulty TPS AND faulty/worn out cam position sensor) and that running the aftermarket TPS in conjunction with the brand new, Mopar cam position sensor (and crank position sensor) might smooth things over. At first, it seemed to work until the issues came back as described above. I will likely grab a new Mopar TPS to round out the complete replacement of all 4 sensors with new Mopar sensors and then look at replacing plugs- beginning with TPS plug. It is comforting in one way to know that I'm on to something- but frustrating in another way to not be able to put my finger on just what that is. Thanks, everyone, for your help!
 

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Discussion Starter · #39 ·
The dealership told me the TPS sensor for my car was discontinued, so they couldn't get one. All the parts stores that carry NGK had to special order one. So. I ordered a Mopar part off eBay. While I'm waiting on it, I went down to the salvage yard and grabbed a TPS sensor out of a donor and grabbed the plug pig tail too. I installed both in the parking lot, and it didn't improve anything. Pretty confusing... :-/
 

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The dealership told me the TPS sensor for my car was discontinued, so they couldn't get one. All the parts stores that carry NGK had to special order one. So. I ordered a Mopar part off eBay. While I'm waiting on it, I went down to the salvage yard and grabbed a TPS sensor out of a donor and grabbed the plug pig tail too. I installed both in the parking lot, and it didn't improve anything. Pretty confusing... :-/
Okay hear me out, I own a 02 SXT - I pulled a TPS sensor out of an 02 Chrysler 300m one time and it actually caused me issues and threw the code p0121. This was because the part number was NOT the same!

Unless it is the same part number and it so happens to also be bad! Or - maybe you're on the path to determining the fault lies else where? (PCM?) You are going to have to wait until your ebay part arrives. Hopefully you ordered the same exact part number!
 
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