Fault code

BMW 5A45 — DKG Clutch 2 Incorrect Pressure

P17A4 · P17A5

Description

BMW fault code 5A45 indicates that the DKG mechatronic unit has detected incorrect hydraulic pressure in the clutch 2 circuit. Clutch 2 operates even-numbered gears (2, 4, 6) in the 7-speed M DCT transmission. When this fault is set, the GS module disables clutch circuit 2, locking out gears 2, 4, and 6. The vehicle enters limp-home mode with only odd gears and reverse available.

Safety warning

Transmission damage risk. Continued driving with active DKG clutch pressure faults can cause accelerated clutch wear or internal hydraulic damage. If the "Transmission malfunction" warning appears, reduce speed and avoid aggressive driving. Diagnosis requires ISTA with DKG-specific test routines — this is not a DIY repair.

This code has 2 variants:

5A45 / P17A4

Pressure too low

Clutch 2 hydraulic pressure below expected threshold

5A45 / P17A5

Pressure too high

Clutch 2 hydraulic pressure above expected threshold

5A45 / P17A4 — Pressure too low

The GS module detected that hydraulic pressure in the clutch 2 circuit is too low during open-loop or closed-loop pressure control. Monitoring conditions match those of the clutch 1 circuit: pressure signal valid, cut-off not at reservoir, driver circuit active. Temperature-dependent detection time: 200 ms above 0°C, 400 ms below −30°C.

Symptoms (5)

Dashboard warning: "Transmission malfunction! Drive gently" (ID 365)
Limp-home mode: gears 2, 4, and 6 locked out (clutch circuit 2 disabled)
Only odd gears (1, 3, 5, 7) and reverse remain available
Harsh or delayed engagement in remaining gears
Possible slipping during clutch 2 engagement attempts before limp-home activates

Common Causes (5)

Defective clutch 2 pressure sensor. If resting pressure reads outside the 0.2–1.8 bar window, the sensor is likely faulty. Both clutch sensors are checked simultaneously.
Internal hydraulic leak in clutch 2 circuit. Worn seals in the mechatronic unit or clutch 2 piston can allow pressure bleed-off.
Failing hydraulic pump or accumulator. Insufficient system pressure affects all circuits but may manifest first on the circuit with tighter tolerances.
Sticking or worn control valve (PV2). The proportional valve for clutch 2 may be underdelivering pressure due to contamination or wear.
Related fault 5A5A present. If the cut-off valve for path 2 is malfunctioning, clutch 2 cannot maintain pressure.

Diagnosis Steps (15)

Precondition: Engine off, ISTA connected.

Read pressure sensor raw data for both clutch 1 and clutch 2. Resting pressure must be between 0.2 and 1.8 bar.
- Outside tolerance → defective sensor. Replace E-module.
- Within tolerance → continue.
Check for related fault 0x5A5A (cut-off path 2). If present, diagnose 5A5A first.
Read fault category:
- Category 0, 2, or 4 (undefined, charging time, or pressure too low) → proceed to leak analysis.
- Category 8 (pressure too high) → see P17A5 variant.
Run pressure leak analysis (precondition: both transmission units in neutral, engine running). Execute three times each:
- Test_Druck_Leck1_01
- Test_Druck_Leck2_01
- Test_Druck_Sys15_01
- Test_Druck_Sysmax_01
Evaluate indices.
- All ≤ 1 → no significant leak. Clear fault and road test.
- Any > 1 → internal hydraulic failure. Transmission replacement required.

Defective pressure sensor: Replace mechatronic E-module.
Internal hydraulic leak (indices > 1): Transmission replacement required. DKG clutch packs are not field-repairable.
Sporadic fault, normal resting pressure: Clear fault, road test, and re-evaluate.
After mechatronic or transmission replacement, run ISTA clutch learning and adaptation reset service functions.
Dealer/specialist repair only — requires ISTA.

5A45 / P17A5 — Pressure too high

The GS module detected that hydraulic pressure in the clutch 2 circuit exceeds the expected range. Excessive pressure risks accelerated wear or damage to the clutch 2 pack. Same monitoring conditions as P17A4.

Symptoms (5)

Dashboard warning: "Transmission malfunction! Drive gently" (ID 365)
Limp-home mode: gears 2, 4, and 6 locked out (clutch circuit 2 disabled)
Only odd gears (1, 3, 5, 7) and reverse remain available
Possible harsh or grabby clutch engagement before limp-home activates
Clutch shudder at low speeds

Common Causes (4)

Sticking control valve (PV2) in the high-pressure position. Contamination or wear causes the valve to deliver excessive pressure.
Defective clutch 2 pressure sensor reading high. Confirmed by checking resting pressure tolerance.
Mechatronic module internal control fault. Electronic issue commanding incorrect pressure targets.
Clutch 2 kiss-point drift. Wear-related adaptation drift causes the GS module to over-command pressure.

Diagnosis Steps (12)

Precondition: Engine off, ISTA connected.

Read pressure sensor raw data. Check resting pressure for both clutches. Expected: 0.2–1.8 bar.
- Outside tolerance → defective sensor. Replace E-module.
- Within tolerance → continue.
Check for related fault 0x5A5A. If present, diagnose first.
Read fault category. For overpressure, category is 8 (pressure too high).
Read frequency counter for fault 0x5A44. Note: ISTA references 0x5A44 for frequency assessment even on clutch 2 overpressure — this counter tracks cumulative overpressure events across both clutch circuits.
Run clutch learning service functions:
- Learn clutch / PV2
- Learn kiss-point
Evaluate result.
- Functions succeed → clear fault and road test.
- Functions fail → proceed to resolution.

Successful clutch re-learn: Clear faults and road test. Monitor for recurrence.
Failed service functions: Replace mechatronic E-module.
High frequency counter with repeated failures: Assess clutch 2 pack condition. Transmission replacement may be required if overpressure caused clutch damage.
Dealer/specialist repair requiring ISTA.

Last updated Mar 28, 2026 · Suggest an edit