P1750 – AT – hydraulic system mechanical malfunction (Honda)

By Reinier (Contact Me)
Last Updated 2023-06-27
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1750

Table of Contents

1. What Does Code P1750 Mean?
2. Where is the P1750 sensor located?
3. What are the common causes of code P1750?
4. What are the symptoms of code P1750?
5. Get Help with P1750

What Does Code P1750 Mean?

OBD II fault code P1750 is a manufacturer-specific trouble code that is defined by carmaker Honda as P1750 – “AT – Hydraulic System Mechanical Malfunction” or sometimes as P1750 – “Mechanical Problem in Hydraulic Control System – A/T Clutch Pressure Control Solenoid Valve”, and is set when the PCM (Powertrain Control Module) detects a mechanical failure or malfunction in a clutch pressure control solenoid valve.

One feature that is common to all automatic transmissions, including automatic transmissions in Honda products is that all automatic transmissions use pressurized transmission fluid to work. In all cases, an engine-driven pressure pump inside the transmission provides pressurized fluid to various parts and components inside the transmission to rearrange sets of planetary gears to create different gear “ratios” that are roughly analogous to the gear ratios in manual transmissions.

We need not delve into the finer details of how automatic transmissions work here but suffice it to say that computer-controlled solenoids direct pressurized fluid into dedicated circuits to affect gearshifts at predetermined points in the engine’s speed range. In practice, pressurized fluid maintains pressure on a clutch pack that typically (but not always) serves two gear ratios. Therefore, when a gear shift is commanded, one solenoid aka “shift solenoid”, opens to relieve the pressure in one circuit, while another shift solenoid directs pressurized fluid into a circuit that serves the next higher or lower gear.

If we assume that all the shift solenoids work as expected, the transmission control module will effect gearshifts in an almost seamless manner by synchronizing the opening and closing of the solenoids with a high degree of precision. If we also assume that all the clutch packs in the transmission are in good condition and that they all work as expected, the re-arrangement of the planetary gear sets in the transmission will occur noiselessly and within specified time limits.

Moreover, in a fully functional transmission, the pressure control solenoids will maintain a specified hydraulic pressure on the clutch pack in use to prevent the individual clutch friction plates from slipping against each other and/or dragging, i.e., not releasing properly when hydraulic pressure is removed from the clutch pack.

However, the normal use of a transmission sometimes causes large quantities of clutch and metal wear particles to enter the hydraulic circuits in the valve body and elsewhere in the transmission. In some cases, these particles can become lodged in pressure control solenoids causing them to bind or stick in their bores, thus preventing them from moving freely. This type of failure is relatively common in transmissions that are not serviced regularly, and when such a failure does occur, the PCM and/or TCM (Transmission Control Module) will interpret the failure as a mechanical failure, and it will set code P1750 and illuminate a warning light as a result.

Where is the P1750 sensor located?

This image shows the location of the clutch pressure control solenoid(s) mounted on the outside of the transmission on a 2004 Honda Accord.

Note that on many newer Honda products, these solenoids may be located inside the transmission, which means that replacing and/or servicing this component requires that the transmission fluid be drained and the oil pan be removed to access the part. As a practical matter, we do not recommend that novice or inexperienced non-professional mechanics attempt this procedure due to the very high likelihood that damage to the transmission could occur. Therefore, we strongly recommend that you seek professional assistance with diagnosing and repairing/resolving any transmission-related issues or trouble codes.

What are the common causes of code P1750?

Some common causes of code P1750 could include one or more of the following, but note that the presence of this code does not necessarily indicate a fault or issue with the clutch control solenoid itself. In many cases, simple wiring issues or defective shift solenoids in the valve body can also cause the code to be set-

• Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors anywhere in the solenoids’ wiring
• Dirty, degraded, or contaminated transmission fluid
• Low transmission fluid level
• Overheated transmission
• Defective or malfunctioning shift solenoid(s)
• Damaged transmission clutch packs
• Defective or malfunctioning engine speed sensor
• Incorrect or sloppy assembly of a rebuilt/repaired transmission
• Failed or failing transmission control module

What are the symptoms of code P1750?

Common symptoms of code P1750 could include one or more of the following-

• Stored trouble code and an illuminated warning light
• Multiple additional codes may be present along with P1750
• The transmission may not select some gears
• The transmission may not select any gear
• The transmission may be locked into one gear
• The transmission may slip severely upon acceleration
• The transmission may overheat severely
• The vehicle will likely be locked into a fail-safe or limp mode that will persist until the fault is corrected, but note that the transmission may require a relearning procedure after a clutch pressure control solenoid replacement

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