Cobra Jet
Well-Known Member
- Thread starter
- #1
So not many are familiar with the S550 steering system, which also falls under the "EPAS" acronym.
EPAS = Electronic Power Steering Assist
PSCM = Power Steering Control Module
The EPAS rack is quite complex. Most don’t know it, but the rack has an internal circuit board an electric motor as well as a rubber belt. Premature failure of those parts could cause multiple steering problems, as well as NVH.
I compiled the below EPAS info a while back; it’s educational for the future when these units do start failing in larger volume and how they could be DIY repaired.
More knowledge is always a good thing, especially with these Mustangs as they become more and more burdened with reliance on cheap electronics....
The below links will point users to the direction they are seeking when trying to trouble shoot the EPAS or if being adventurous and wanting to mess with the PSCM coding.
---
F150 EPAS thread that shows As Built info (so far, no one on this site has attempted to supply S550 EPAS "As Built" info like noted in the F150 link. It does exist In the S550's too, anyone up to the challenge?):
https://www.f150forum.com/f118/forscan-pscm-epas-changes-434605/
---
S550 PSCM Reflash attempt by user @Dragonheart:
https://www.mustang6g.com/forums/th...ategies-calibrations-vbf.112549/#post-2392564
---
LOSS of Power Steering:
https://www.mustang6g.com/forums/th...ower-in-their-steering-while-on-track.127352/
---
EPAS "feel" and other options for rack changes:
https://www.mustang6g.com/forums/th...g-ratio-response-for-s550.97969/#post-2144992
---
Aside from an EPAS rack being damaged either externally or internally, the rack not only has a motor inside of it, but also circuit board and an actual rubber belt. The rubber belt is serviceable. So if the motor or circuit board isn’t damaged, it could be a simple broken belt or the belt jumped off the cogged gear from the impact. See here:
https://www.mustang6g.com/forums/threads/help-identifying-eps-belt-size.127584/#post-2642940
Yes, there is an internal power steering belt (most do not even know it exists). Above link contains pics and belt sizing info.
---
Locked EPAS units; last post update in this thread says the OP found there was a loose connection in a harness which had created a fault (no steering).
https://www.mustang6g.com/forums/th...ower-in-their-steering-while-on-track.127352/
This one touches on corroded battery cables leading to malfunctioning EPAS:
https://www.mustang6g.com/forums/threads/need-to-replace-my-rack.132063/#post-2724002
This thread has good troubleshooting info if needed:
https://www.mustang6g.com/forums/th...king-help-from-a-tech-ideas-on-causes.120707/
---
This thread has some insight to what is involved with removing the rack for repair effort:
https://www.mustang6g.com/forums/threads/need-help-steering-rack-replacement.129096/
---
This thread has some excellent TECH repair and photos of the EPAS with it apart and where the EPAS circuitry is located; thread also discusses FORSCAN flashes:
https://www.mustang6g.com/forums/th...ategies-calibrations-vbf.112549/#post-2611462
---
EPAS & other module stand alone discussion:
https://www.mustang6g.com/forums/threads/abs-epas-bcm-functionality-with-standalone.160543/
---
GT350 EPAS unit:
https://www.mustang6g.com/forums/threads/fp350s-epas-steering-rack.141992/
---
2018 PSCM Update via SSM 46997 direction:
https://www.mustang6g.com/forums/th...g-pscm-calibration-update.99829/#post-2198141
---
Steering Mode discussion:
https://www.mustang6g.com/forums/threads/steering-wheel-mode.101153/
---
Advance Track issues tied to PSCM:
https://www.mustang6g.com/forums/threads/advancetrac-issue.119830/page-2#post-2675638
---
Steering Angle Sensor and LKA discussion:
https://www.mustang6g.com/forums/threads/steering-angle-sensor-reset-with-alignment.162762/
---
Steering assist fault analysis:
https://www.mustang6g.com/forums/th...ch-ideas-on-causes.120707/page-3#post-2523951
---
Steering assist malfunction (car won't start):
https://www.mustang6g.com/forums/th...malfunction-wouldnt-start.58046/#post-1365778
---
Excellent EPAS article from Motor.com:
https://www.motor.com/magazine-summary/ford-epas-steering-you-straight-march-2019/
---
Cortex Racing's "EPAS Stimulator Module":
https://cortexracing.com/product/ep...-2015-2020-s550-ford-mustang-f150-and-raptor/
Thread by Cortex discussing purpose:
https://trackmustangsonline.com/threads/cortex-epas-steering-simulator.15283/
---
PSCM Harness and checking of connections (GSB00048) attached pdf below.
EPAS = Electronic Power Steering Assist
PSCM = Power Steering Control Module
The EPAS rack is quite complex. Most don’t know it, but the rack has an internal circuit board an electric motor as well as a rubber belt. Premature failure of those parts could cause multiple steering problems, as well as NVH.
I compiled the below EPAS info a while back; it’s educational for the future when these units do start failing in larger volume and how they could be DIY repaired.
More knowledge is always a good thing, especially with these Mustangs as they become more and more burdened with reliance on cheap electronics....
The below links will point users to the direction they are seeking when trying to trouble shoot the EPAS or if being adventurous and wanting to mess with the PSCM coding.
---
F150 EPAS thread that shows As Built info (so far, no one on this site has attempted to supply S550 EPAS "As Built" info like noted in the F150 link. It does exist In the S550's too, anyone up to the challenge?):
https://www.f150forum.com/f118/forscan-pscm-epas-changes-434605/
---
S550 PSCM Reflash attempt by user @Dragonheart:
https://www.mustang6g.com/forums/th...ategies-calibrations-vbf.112549/#post-2392564
---
LOSS of Power Steering:
https://www.mustang6g.com/forums/th...ower-in-their-steering-while-on-track.127352/
---
EPAS "feel" and other options for rack changes:
https://www.mustang6g.com/forums/th...g-ratio-response-for-s550.97969/#post-2144992
---
Aside from an EPAS rack being damaged either externally or internally, the rack not only has a motor inside of it, but also circuit board and an actual rubber belt. The rubber belt is serviceable. So if the motor or circuit board isn’t damaged, it could be a simple broken belt or the belt jumped off the cogged gear from the impact. See here:
https://www.mustang6g.com/forums/threads/help-identifying-eps-belt-size.127584/#post-2642940
Yes, there is an internal power steering belt (most do not even know it exists). Above link contains pics and belt sizing info.
---
Locked EPAS units; last post update in this thread says the OP found there was a loose connection in a harness which had created a fault (no steering).
https://www.mustang6g.com/forums/th...ower-in-their-steering-while-on-track.127352/
This one touches on corroded battery cables leading to malfunctioning EPAS:
https://www.mustang6g.com/forums/threads/need-to-replace-my-rack.132063/#post-2724002
This thread has good troubleshooting info if needed:
https://www.mustang6g.com/forums/th...king-help-from-a-tech-ideas-on-causes.120707/
---
This thread has some insight to what is involved with removing the rack for repair effort:
https://www.mustang6g.com/forums/threads/need-help-steering-rack-replacement.129096/
---
This thread has some excellent TECH repair and photos of the EPAS with it apart and where the EPAS circuitry is located; thread also discusses FORSCAN flashes:
https://www.mustang6g.com/forums/th...ategies-calibrations-vbf.112549/#post-2611462
---
EPAS & other module stand alone discussion:
https://www.mustang6g.com/forums/threads/abs-epas-bcm-functionality-with-standalone.160543/
---
GT350 EPAS unit:
https://www.mustang6g.com/forums/threads/fp350s-epas-steering-rack.141992/
---
2018 PSCM Update via SSM 46997 direction:
https://www.mustang6g.com/forums/th...g-pscm-calibration-update.99829/#post-2198141
---
Steering Mode discussion:
https://www.mustang6g.com/forums/threads/steering-wheel-mode.101153/
---
Advance Track issues tied to PSCM:
https://www.mustang6g.com/forums/threads/advancetrac-issue.119830/page-2#post-2675638
---
Steering Angle Sensor and LKA discussion:
https://www.mustang6g.com/forums/threads/steering-angle-sensor-reset-with-alignment.162762/
---
Steering assist fault analysis:
https://www.mustang6g.com/forums/th...ch-ideas-on-causes.120707/page-3#post-2523951
---
Steering assist malfunction (car won't start):
https://www.mustang6g.com/forums/th...malfunction-wouldnt-start.58046/#post-1365778
---
Excellent EPAS article from Motor.com:
https://www.motor.com/magazine-summary/ford-epas-steering-you-straight-march-2019/
---
Cortex Racing's "EPAS Stimulator Module":
https://cortexracing.com/product/ep...-2015-2020-s550-ford-mustang-f150-and-raptor/
Thread by Cortex discussing purpose:
https://trackmustangsonline.com/threads/cortex-epas-steering-simulator.15283/
---
PSCM Harness and checking of connections (GSB00048) attached pdf below.
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Last edited:
