I have a 94 Bronco with automatic trans with overdrive. For no rhyme or reason it will sometimes drop into neutral when driving. I have to let off gas to drop RPM to have it go back into gear. When it starts it does it over and over sometimes so bad I limp home let it sit for a couple of hours and off I go with no issue. It was doing it last year about this same time. I broke down it slammed into gear and something broke inside so I had trans rebuilt. it can go days sometimes a week and a half with no slips. Puzzled and ideas
94 auto Transmission drops into neutral
- Thread starter pxbris
- Start date
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yo pxbris,
WELCOME!
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
http://broncozone.com/topic/14269-code-reader/page__pid__74587__mode__threaded
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.
Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.
Do Key On Engine Off (KOEO) portion first.
Look Codes up in my broncolinks.com site using the new Search function.
And Post em here according to:
KOEO
&
KOER
Manual Lever Position (MLPS) Nagging Neutral Nonsense & Pinpoint Test; "...One of the most-difficult problems to diagnose on a Ford car or truck is a sudden neutral condition while the vehicle is cruising in 4th gear. Now this can have a number of causes, depending on which transmission is in the car or truck, but the cause we are going to discuss here is that #(~! *&A% Manual Lever Position Sensor – that’s right, the old MLPS. This sensor is responsible for more malfunctions than any other sensor in the system, and the kicker is that it seldom stores a code 67 or 634. Actually there is a standing joke in our industry that says, “You got a problem with a Ford, change the MLPS; it fixes everything,” which ain’t that funny because it’s not that far from the truth. Some of the problems the MLPS can cause are wrong gear starts, TCC hunting, no 4th gear, engine stalling, high or erratic line pressure and the problem that this article is about – a sudden neutral condition. Whether the MLPS is attached to an E4OD, AXODE, AODE or CD4E, the operating characteristics are the same. What that means is the MLPS is classified as a step-down resistor. The MLPS is supplied 5 volts from the computer as a reference voltage, and as the shift lever is moved from park toward manual low, the voltage in each gear-shift position will decrease as shown in Figure 1. The MLPS also can be checked for correct resistance, also shown in Figure 1. This way, if the resistance checked good on the bench but the voltage does not check good in the vehicle, you know there must be a wiring or ground problem. I know what you are thinking: You replace the MLPS on every job you do, so why should you check the resistance on a new part? Well, that’s fine, but one thing has become very clear lately: NEW DOES NOT MEAN GOOD! Now, let’s get to the meat of the problem. As you can see in Figure 1, the voltage in the drive/overdrive position can be 1.88 to 2.30 volts. The O.D. Cancel button, on those vehicles equipped with one, has no effect on the voltage seen in the drive position, nor does it matter whether the vehicle has a gas or diesel engine. This would be the voltage seen in the D or D position if it were available on the scan-tool screen in the data mode. Unfortunately, this information is not always available, and this “glitch” may occur faster than the scan-tool’s update capability so the voltage jump would be missed. Therefore, a digital multimeter must be used to monitor this voltage. This is of the utmost importance in diagnosing the sudden-neutral condition. This voltage should be monitored when the neutral condition occurs by placing the multimeter’s positive lead to computer terminal 30 if it is an EEC-IV system, as illustrated in Figure 2, or to terminal 64 if it is an EEC-V system. This wire is light blue/yellow on all applications except vehicles with the CD4E. On these the signal wire is red/black. Now, here is where this gets a little involved. The negative lead of the multimeter should be placed at the MLPS signal-return ground terminal at the MLPS. The reason is that the ground circuit for the MLPS can be shared by as many as FIVE other sensors, as seen in the wiring diagram in Figure 2. This means that there are factory splices in this ground circuit. If you check this ground at computer terminal 46 for the EEC- IV or computer terminal 91 for the EEC-V, the ground may check good but could be bad at the MLPS if there is a problem on the MLPS side of the splice, as also can be seen in the wiring diagram in Figure 2. The ground-circuit wire for 1989-90 F- and E-series trucks is black/white; all other vehicles use a gray/red ground wire except for CD4E applications, on which the ground wire is black/blue. Once the multimeter is connected to these circuits, as seen in Figure 3, place the meter where it can be seen while driving. When the transmission suddenly neutrals, be sure to have someone observe the multimeter, or use the meter’s MIN/MAX feature to record the highest and lowest voltage readings that occurred in the circuit. If the voltage jumps toward 3 volts as shown in Figure 3, and at that very moment the transmission neutrals, either the MLPS is faulty or the MLPS ground circuit is poor. Under normal conditions, this voltage reading SHOULD NOT CHANGE! When the voltage jumps toward 3 volts, this indicates a neutral-shift- lever position to the processor. This confuses the computer’s logic system, and therefore the computer is unable to fire the shift solenoids correctly (I think), and – BAM – you have a sudden-neutral condition. Why does the voltage jump because of a poor ground? The poorer the ground, the higher the resistance will be in that ground circuit. The higher resistance will cause the voltage in the overdrive or drive position to rise toward the 5-volt reference voltage, much like putting a bend in a garden hose would raise the pressure in the hose behind the bend. Ground- circuit integrity can be verified by placing the positive multimeter lead to the MLPS ground terminal at the MLPS and the negative multimeter lead to the negative battery post, as seen in Figure 4. With the multimeter set to DC volts and the engine running, the maximum voltage should be 0.1 volt. If more than 0.1 volt is seen on this ground circuit, it is NOT a good ground. In order to correct this condition, cut the ground wire close to the MLPS, attach it to a known good ground and recheck as previously described. Two things must be remembered here. One is that the return electricity will seek the path of least resistance. This path MUST be the ground circuit, NOT your multimeter. That’s why you should see a maximum of 0.1 volt on any 5-volt-reference ground circuit; 0.3 is acceptable on a 12-volt-reference voltage supply. The second thing to remember is that most electrical- fault phone calls I receive on the ATSG helpline are ground-related problems, so be sure to use the voltage-drop method of checking grounds as described. It may help to prevent you from falling into this trap..." See Diagrams & instructions
Source: by Pete L at http://www.transonline.com/transdigest/magazines/1998-10/Shift%20Pointers/index.html
Do the MLPS Test
The alternative is to back-probe the MLP line with a volt meter while in Park, and set it to between 4.277 and 4.736 volts (ideally at 4.5065V, right in the middle of the two limits). As a "double-check" afterward, pull the lever down to 1st gear, and again test the MLP voltage; it should be between 0.293 and 1.167 volts, ideally in the middle at 0.73V.
If the MLPS needs replacement, use Ford part # E5TZ-7A247-A. This kit includes a new style harness connector. You must replace the connector to use the new MLPS. By sliding the old wire separator from the original connector up the harness you can leave it in place as you install the new connector. This helps to keep the wires in their original location. Make sure you clean the harness connector with brake clean and apply some dielectric grease to the pins. This will ensure a good connection. Use Permatex part # 67V (dielectric tune-up grease). You can get it at most auto parts stores..."
Use these diagrams to help
Source: by fordbronco1995 ("JUICE") at
WELCOME!
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
http://broncozone.com/topic/14269-code-reader/page__pid__74587__mode__threaded
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.
Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.
Do Key On Engine Off (KOEO) portion first.
Look Codes up in my broncolinks.com site using the new Search function.
And Post em here according to:
KOEO
&
KOER
Manual Lever Position (MLPS) Nagging Neutral Nonsense & Pinpoint Test; "...One of the most-difficult problems to diagnose on a Ford car or truck is a sudden neutral condition while the vehicle is cruising in 4th gear. Now this can have a number of causes, depending on which transmission is in the car or truck, but the cause we are going to discuss here is that #(~! *&A% Manual Lever Position Sensor – that’s right, the old MLPS. This sensor is responsible for more malfunctions than any other sensor in the system, and the kicker is that it seldom stores a code 67 or 634. Actually there is a standing joke in our industry that says, “You got a problem with a Ford, change the MLPS; it fixes everything,” which ain’t that funny because it’s not that far from the truth. Some of the problems the MLPS can cause are wrong gear starts, TCC hunting, no 4th gear, engine stalling, high or erratic line pressure and the problem that this article is about – a sudden neutral condition. Whether the MLPS is attached to an E4OD, AXODE, AODE or CD4E, the operating characteristics are the same. What that means is the MLPS is classified as a step-down resistor. The MLPS is supplied 5 volts from the computer as a reference voltage, and as the shift lever is moved from park toward manual low, the voltage in each gear-shift position will decrease as shown in Figure 1. The MLPS also can be checked for correct resistance, also shown in Figure 1. This way, if the resistance checked good on the bench but the voltage does not check good in the vehicle, you know there must be a wiring or ground problem. I know what you are thinking: You replace the MLPS on every job you do, so why should you check the resistance on a new part? Well, that’s fine, but one thing has become very clear lately: NEW DOES NOT MEAN GOOD! Now, let’s get to the meat of the problem. As you can see in Figure 1, the voltage in the drive/overdrive position can be 1.88 to 2.30 volts. The O.D. Cancel button, on those vehicles equipped with one, has no effect on the voltage seen in the drive position, nor does it matter whether the vehicle has a gas or diesel engine. This would be the voltage seen in the D or D position if it were available on the scan-tool screen in the data mode. Unfortunately, this information is not always available, and this “glitch” may occur faster than the scan-tool’s update capability so the voltage jump would be missed. Therefore, a digital multimeter must be used to monitor this voltage. This is of the utmost importance in diagnosing the sudden-neutral condition. This voltage should be monitored when the neutral condition occurs by placing the multimeter’s positive lead to computer terminal 30 if it is an EEC-IV system, as illustrated in Figure 2, or to terminal 64 if it is an EEC-V system. This wire is light blue/yellow on all applications except vehicles with the CD4E. On these the signal wire is red/black. Now, here is where this gets a little involved. The negative lead of the multimeter should be placed at the MLPS signal-return ground terminal at the MLPS. The reason is that the ground circuit for the MLPS can be shared by as many as FIVE other sensors, as seen in the wiring diagram in Figure 2. This means that there are factory splices in this ground circuit. If you check this ground at computer terminal 46 for the EEC- IV or computer terminal 91 for the EEC-V, the ground may check good but could be bad at the MLPS if there is a problem on the MLPS side of the splice, as also can be seen in the wiring diagram in Figure 2. The ground-circuit wire for 1989-90 F- and E-series trucks is black/white; all other vehicles use a gray/red ground wire except for CD4E applications, on which the ground wire is black/blue. Once the multimeter is connected to these circuits, as seen in Figure 3, place the meter where it can be seen while driving. When the transmission suddenly neutrals, be sure to have someone observe the multimeter, or use the meter’s MIN/MAX feature to record the highest and lowest voltage readings that occurred in the circuit. If the voltage jumps toward 3 volts as shown in Figure 3, and at that very moment the transmission neutrals, either the MLPS is faulty or the MLPS ground circuit is poor. Under normal conditions, this voltage reading SHOULD NOT CHANGE! When the voltage jumps toward 3 volts, this indicates a neutral-shift- lever position to the processor. This confuses the computer’s logic system, and therefore the computer is unable to fire the shift solenoids correctly (I think), and – BAM – you have a sudden-neutral condition. Why does the voltage jump because of a poor ground? The poorer the ground, the higher the resistance will be in that ground circuit. The higher resistance will cause the voltage in the overdrive or drive position to rise toward the 5-volt reference voltage, much like putting a bend in a garden hose would raise the pressure in the hose behind the bend. Ground- circuit integrity can be verified by placing the positive multimeter lead to the MLPS ground terminal at the MLPS and the negative multimeter lead to the negative battery post, as seen in Figure 4. With the multimeter set to DC volts and the engine running, the maximum voltage should be 0.1 volt. If more than 0.1 volt is seen on this ground circuit, it is NOT a good ground. In order to correct this condition, cut the ground wire close to the MLPS, attach it to a known good ground and recheck as previously described. Two things must be remembered here. One is that the return electricity will seek the path of least resistance. This path MUST be the ground circuit, NOT your multimeter. That’s why you should see a maximum of 0.1 volt on any 5-volt-reference ground circuit; 0.3 is acceptable on a 12-volt-reference voltage supply. The second thing to remember is that most electrical- fault phone calls I receive on the ATSG helpline are ground-related problems, so be sure to use the voltage-drop method of checking grounds as described. It may help to prevent you from falling into this trap..." See Diagrams & instructions
Source: by Pete L at http://www.transonline.com/transdigest/magazines/1998-10/Shift%20Pointers/index.html
Do the MLPS Test
The alternative is to back-probe the MLP line with a volt meter while in Park, and set it to between 4.277 and 4.736 volts (ideally at 4.5065V, right in the middle of the two limits). As a "double-check" afterward, pull the lever down to 1st gear, and again test the MLP voltage; it should be between 0.293 and 1.167 volts, ideally in the middle at 0.73V.
If the MLPS needs replacement, use Ford part # E5TZ-7A247-A. This kit includes a new style harness connector. You must replace the connector to use the new MLPS. By sliding the old wire separator from the original connector up the harness you can leave it in place as you install the new connector. This helps to keep the wires in their original location. Make sure you clean the harness connector with brake clean and apply some dielectric grease to the pins. This will ensure a good connection. Use Permatex part # 67V (dielectric tune-up grease). You can get it at most auto parts stores..."
Use these diagrams to help
Source: by fordbronco1995 ("JUICE") at
Last edited by a moderator:
BroncoJoe19
Active member
X2 ^ on the MLPS.
