OBD-II Code
P1735
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$50–$1,200
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P1735 is a Ford-specific code meaning the First Gear Switch circuit has failed — on the 5R55E/5R55W/5R55S and certain 4R70W variants, the trans uses a dedicated 1st-gear position switch (separate from the MLPS) that confirms the gearbox is mechanically engaged in 1st when the PCM commands 1st gear, primarily for the lockup/coastdown logic and the manual-1 enforcement.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP1735 is a Ford-specific code meaning the First Gear Switch circuit has failed — on the 5R55E/5R55W/5R55S and certain 4R70W variants, the trans uses…
P1735 is a Ford-specific code meaning the First Gear Switch circuit has failed — on the 5R55E/5R55W/5R55S and certain 4R70W variants, the trans uses a dedicated 1st-gear position switch (separate from the MLPS) that confirms the gearbox is mechanically engaged in 1st when the PCM commands 1st gear, primarily for the lockup/coastdown logic and the manual-1 enforcement. Circuit failure can be open, shorted to ground, or shorted to power.
Cheapest-first ladder
- Pull the harness connector at the trans-case bulkhead and inspect for ATF migration, corrosion, and backed-out pins — same failure path as every other internal-harness Ford trans code ($0, 10 min).
- Verify the 1st-gear switch signal with KOEO and the scan tool: the switch should pull low (<0.5V) or high (>10V) depending on application when the manual valve is in the M1 detent, and the opposite state in all other positions.
- Resistance-check the switch contacts from the case-external connector — open circuit in M1 confirms the switch or its internal harness is open; if the switch tests good in M1 but the code persists, the fault is between the case connector and the PCM.
- Inspect for any recent valve-body work — the 1st-gear switch is often disturbed during valve-body service and can be reinstalled with a pinched O-ring or mis-clocked, causing intermittent contact. Expensive-misdiagnosis caveat: P1735 on a 5R55-series gearbox after a valve-body service is almost always installation-related, not a failed switch — don't order a new switch until you've pulled the pan, inspected the valve-body-to-case interface, and confirmed the switch terminal isn't grounded by a misrouted internal harness.
Vehicle-specific patterns1996-2003 Ford Explorer/Mountaineer with the 5R55E and 1997-2011 Ford Ranger with the 5R55E throws P1735 from internal harness contamination and from…
- 1996-2003Ford Explorer/Mountaineer with the 5R55E and 1997-2011 Ford Ranger with the 5R55E throws P1735 from internal harness contamination and from the 1st-gear switch contact wearing flat after high-mileage manual-1 use (off-road and trailering).
- 1996-2010F150 and 1996-2014 E150/E250/E350 vans with the AODE/4R70W (early variants with the discrete 1st-gear switch) see P1735 from the same internal-harness ATF migration path that drives P1701/P1702/P1716.
- 1996-2010Mustang with the AODE/4R70W sees P1735 less often because the M1 manual range gets little use.
- 1996-2011Crown Vic Police Interceptor sees P1735 in service from heavy stop-and-go fleet cycling.
Estimated repair$50 to $1,200.
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