P103C and no brake boost in reverse?

[samayeam]

We have been having a random issue only on reverse upon first startup of the day. Go to apply brakes after releasing while in reverse and the pedal hardly moves…stiff as hell. Truck keeps backing up until you stand on the pedal, at which time the abs pump kicks in and it feels as if power brake assist is back.
No dash lights, chimes, or warnings. Checked for codes a couple of times after this occurs (wife drives it more than me) and it seems to always have P103C “Aspirator Valve control circuit open.” Clear code and it comes back sometime later. Code can be in and not have the physical problem when reversing.

Questions:

1. What and where the heck is the “aspirator valve?”. Something to do with brake booster?

2. Anyone else experience either the code or the no power assist in reverse with abs kicking in when assist comes back (abs cycling even though FAR from locking up brakes)?

we have experienced other power assist brake issues previously that were found to be related to a Demco stay-n-play duo supplemental brake system (for flat towing the ranger) allowing vacuum to be bled off, but that created bells, chimes, warning displays, dash lights, and other codes that actually mentioned brake system. Changing the way the supplemental vacuum pump tied into the booster (per Demco) solved that issue.

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[airline tech]

I cannot find any specific codes for P103C in the manual. But that code is related to Brake Booster Vacuum, I suspect vacuum is bleeding down overnight or bad sensor. I would look at the vacuum line going into the booster and check any electrical connectors attaching at the booster, the ranger has added electronics to the booster system of yesteryear.



Vacuum On Demand System

Vehicles equipped with a 2.3L engine supply vacuum to the brake booster through the use of a valve solenoid and an aspirator in the brake booster vacuum tube. When the ABS module detects a low vacuum condition in the brake booster, a message is sent to the PCM requesting additional vacuum. The PCM responds by opening the valve solenoid which allows the engine to draw air from the brake booster, increasing vacuum in the booster. Once the vacuum in the booster has reached the required level, the ABS module stops sending the message and the PCM closes the valve solenoid.


This is the only test I could find, are you sure the code is correct.

Component Test- Brake Booster

1. Disconnect the brake booster vacuum sensor/check valve from the brake booster and connect a suitable vacuum/pressure tester to the booster side of the vacuum sensor/check valve.
2. Apply the parking brake, start the engine and place the transmission in NEUTRAL.
   • Allow the engine to reach normal operating temperature.
3. Verify that vacuum is available at the vacuum sensor/check valve with engine running at normal idle speed.
   • The vacuum gauge should read between 51-74 kPa (15-22 in-Hg).
   • If specified vacuum is available, stop the engine, connect the vacuum sensor/check valve and continue with Step 5.
   • If specified vacuum is not available, continue with Step 4.
4. Disconnect the vacuum sensor/check valve from the vacuum hose and verify that the specified vacuum is available at the hose with the engine at idle speed and the transmission in NEUTRAL.
   • If specified vacuum is available, stop the engine, install a new check valve and continue with Step 5.
   • For vehicles equipped with a brake vacuum pump, if specified vacuum is not available, inspect the vacuum hose and install new as necessary. If the vacuum hose is OK, install a new vacuum pump.
   • For vehicles not equipped with a brake vacuum pump, if specified vacuum is not available, stop the engine, connect the vacuum hose to the check valve and diagnose the no/low vacuum condition. Carry out the Intake Manifold Vacuum Test.
     REFER to: Engine (303-00 Engine System - General Information, Diagnosis and Testing) .
5. Apply the brake pedal several times to exhaust all vacuum from the system.
6. Apply the brake pedal and hold it in the applied position. Start the engine and verify that the brake pedal moves downward after the engine starts.
   • If the brake pedal moves, the brake booster is operating correctly.
   • If the brake pedal does not move, install a new brake booster.
     REFER to: Brake Booster (206-07 Power Brake Actuation, Removal and Installation) .
7. Operate the engine a minimum of 20 seconds at idle. Stop the engine and let the vehicle stand for 10 minutes, then apply the brake pedal. The brake pedal feel should be the same as that noted with the engine operating.
   • If the brake pedal feels hard (no power assist), install a new brake booster vacuum sensor/check valve and retest.
   • If condition still exists, install a new brake booster.
     REFER to: Brake Booster (206-07 Power Brake Actuation, Removal and Installation) .
     
     
   • If the brake pedal feels the same as noted with the engine operating, the vacuum sensor/check valve is functioning properly.

 

[airline tech]

Item # 13 is the sensor that is triggering the code, for Open Circuit, check connector and wiring.
It measures vacuum in the booster.

 

[samayeam]

Item # 13 is the sensor that is triggering the code, for Open Circuit, check connector and wiring.
It measures vacuum in the booster.

Thank you for the assist.

Item 13 is a sensor and not a valve correct? The revised Demco kit has you hook up essentially a T in place of #13 that relocates #13 but the other side of the T goes to the Demco vacuum pump.

Prior to putting in the revised T at bottom of booster - Demco vacuum pump was T-d into booster by splicing into #14 and we got plenty of low vacuum related codes and faults - complete with brakes going hard while driving for long highway stretches without brake application. I replaced the entire #14 assembly with a new one and installed the new T at the bottom - effectively relocating #13. Truck was fine for probably 3k miles (at 12k presently) until this recent issue.

I likely won't be able to go through the procedure posted for a bit. Just had laparoscopic hernia repair surgery and feels like I'm being continually knifed in my belly fat if I try to move around to much. As soon as I can, I'll check to see if the sensor somehow came unplugged - but if it was truly open circuit - I think I'd be getting a low vacuum code too? Certainly had those prior to relocating the T.

Oh and BTW, confident code is P103C. Using blue drive bluetooth OBD reader as I haven't jumped into FORSCAN yet. We were already living on the road full time by the time we finally got the Ranger and ordering stuff (the right OBD dongle) has been a challenge due to no physical address and our style of travel not being real firm beyond 3-4 days out most of the time.

 

[airline tech]

Yes, Item #13 is listed as a sensor and #14 is a Vacuum Tube Assy, If you can put the system back to original factory and see if problem goes away, that way you can eliminate the Demco add on vs actual issue on the truck side.
As it may be the Demco add on causing the sensor to read inaccurately and or bleeding off when it's not commanded to do so. I am unfamiliar with how that add on works, but since you relocated the sensor check and ensure the wiring is intact and not touching a point anywhere where it can vibrate and chafe against any part, this may be the issue being that's it is intermittent, plus check and ensure that the sensor is secure as if it is vibrating around the connector is also and may be causing the connector to move, thus lose connection.

 

[samayeam]

I had a moment where I thought I’d be okay enough to take a peak under the hood…mostly because I fortunately installed hood lift struts about 2 months ago. Without lift struts, doubt I’d be able to lift the hood and the prop rod right now.

Anyway, the relocated vacuum sensor was properly connected. No signs of wire damage and all joints in tubing appeared as they should. Then I began to wonder again just what the heck an Aspirator control valve is and where it would be located. And then I saw it…a connector dangling loose from one of the components in the #14 assembly pictured. Reconnected, cleared codes and checked codes again as the wife was driving.

So far code has not come back…but only a couple drive cycles since. as the stiff pedal in reverse thing was totally random and infrequent, not quite going to call victory on that just yet.

 

[Kobey]

Hi everyone, first post here. I may be able to add a little for anyone else having vacuum boost problems.

My 2019 started having issues last year. A couple of times on the way home from work my "Check Brake System" alert went off. The brakes worked fine and after restarting the brake indicator light would go out. I figured it was just an occasional glitch with the computer and didn't worry too much about it.

Then I went on the interstate and at speeds over 65 mph, the alert will come on, sometimes immediately, other times it could take almost an hour at that speed to activate it. If I hit the brakes at the higher speed, I have no vacuum assist until I reduce my speed a little.

Recently, I've noticed the same thing the OP describes, loss of assist in reverse occasionally after startup. So the two issues may be symptoms of the same problem.
If I hold down the brake pedal and turn off the truck, the pedal comes up within seconds.

So I'm thinking it is probably one of two things, the vacuum hose assembly or the booster itself. Any thoughts or insight?

 

[Trigganometry]

Hi everyone, first post here. I may be able to add a little for anyone else having vacuum boost problems.

My 2019 started having issues last year. A couple of times on the way home from work my "Check Brake System" alert went off. The brakes worked fine and after restarting the brake indicator light would go out. I figured it was just an occasional glitch with the computer and didn't worry too much about it.

Then I went on the interstate and at speeds over 65 mph, the alert will come on, sometimes immediately, other times it could take almost an hour at that speed to activate it. If I hit the brakes at the higher speed, I have no vacuum assist until I reduce my speed a little.

Recently, I've noticed the same thing the OP describes, loss of assist in reverse occasionally after startup. So the two issues may be symptoms of the same problem.
If I hold down the brake pedal and turn off the truck, the pedal comes up within seconds.

So I'm thinking it is probably one of two things, the vacuum hose assembly or the booster itself. Any thoughts or insight?

Not sure if you ever saw this thread but it definitely does make a difference https://www.ranger5g.com/forum/threads/fix-your-mushy-brakes.15581/

 

[Kobey]

Not sure if you ever saw this thread but it definitely does make a difference https://www.ranger5g.com/forum/threads/fix-your-mushy-brakes.15581/

Thanks for that thread link. The problem I have is the opposite of a mushy pedal, but now I know why I once found myself at the second window at McDonalds when I looked back up after digging for change at the first window. Once I get the vacuum problem fixed, I might have to look into doing that bleed procedure to try and firm them up.

 

[samayeam]

Hi everyone, first post here. I may be able to add a little for anyone else having vacuum boost problems.

My 2019 started having issues last year. A couple of times on the way home from work my "Check Brake System" alert went off. The brakes worked fine and after restarting the brake indicator light would go out. I figured it was just an occasional glitch with the computer and didn't worry too much about it.

Then I went on the interstate and at speeds over 65 mph, the alert will come on, sometimes immediately, other times it could take almost an hour at that speed to activate it. If I hit the brakes at the higher speed, I have no vacuum assist until I reduce my speed a little.

Recently, I've noticed the same thing the OP describes, loss of assist in reverse occasionally after startup. So the two issues may be symptoms of the same problem.
If I hold down the brake pedal and turn off the truck, the pedal comes up within seconds.

So I'm thinking it is probably one of two things, the vacuum hose assembly or the booster itself. Any thoughts or insight?

So I had the same problem of no power assist while driving at Hwy speeds. Very similar. Mine ended up being a vacuum leak associated with the install of a Demco stay n play duo supplemental braking system to enable flat towing of the ranger.

to rectify, I changed where the supplemental vacuum pump tied into the brake booster. While I was at it, I replaced the OEM vacuum line assembly to the brake booster that was hacked into for original tie in of the supplemental brake system.

No power brakes in reverse also threw the code for Aspirator valve. Once someone helped me figure out which component that was, I found it disconnected. Reconnected it and problem free for over 5k miles now.

so, if you don’t have a supplemental brake system tied into your booster - I’d scan it for codes, inspect all vacuum lines associated with the booster, and verify the booster vacuum sensor at bottom of booster is adequately seated.

 

[Kobey]

Thanks, I'm thinking I should probably replace the vacuum line first since that looks like a 15 minute job. I hope it isn't the booster. That looks like it might be next to impossible to remove without removing the lines on the master cylinder.

 

[Kobey]

It looks like Bronco's may be having the same issue and may even have a recall to replace the vacuum tube. The part number is very close, KB3Z-2420-A for the Ranger and MB3Z-2420-F for the Bronco. Guess there haven't been enough complaints on the Ranger to get any action on it.

 

[Kobey]

Update: Changed the vacuum hose assembly, didn't solve the problem. Now I'm having the shudder problem, so I ordered the part to hopefully fix that. Bought a more advanced code reader and it shows a P050F-00 (Brake assist vacuum too low) I'll have to troubleshoot the vacuum system next and try to figure out if it's a bad booster or somewhere else. Maybe I'll get lucky and the EGR sensor will fix both problems.

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