P1594: Automatic Transmission Diagnosis Input Signal Circuit Malfunction

SUBARU BMW DODGE JEEP PLYMOUTH PONTIAC

Severity

Medium

System

Manufacturer-Specific Powertrain

Last reviewed: Jan 1, 0001 Last updated: Jan 1, 0001

Methodology: We combine code standards with complaint and reliability patterns, then review for clear, vehicle-first diagnosis steps.

Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

What Does P1594 Mean?

P1594 is a manufacturer-specific diagnostic trouble code: Automatic Transmission Diagnosis Input Signal Circuit Malfunction. This code applies to SUBARU, BMW, DODGE, JEEP, PLYMOUTH vehicles. Unlike generic OBD-II codes, manufacturer-specific codes are defined by the vehicle maker and may only apply to certain makes and models.

Symptoms of P1594

⚠️ Check Engine Light (MIL) illuminated
⚠️ Erratic Automatic Transmission Diagnosis Input Signal readings
⚠️ Related system operating intermittently
⚠️ Reduced engine performance

Common Causes

🔍 Wiring issue in Automatic Transmission Diagnosis Input Signal circuit (damaged, chafed, or corroded)
🔍 Faulty Automatic Transmission Diagnosis Input Signal connector or terminal
🔍 Failed Automatic Transmission Diagnosis Input Signal
🔍 ECM/PCM connection issue

Frequently Asked Questions

What does P1594 mean?

P1594 indicates: Automatic Transmission Diagnosis Input Signal Circuit Malfunction. The vehicle's computer has detected that the Automatic Transmission Diagnosis Input Signal is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P1594?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P1594 for extended periods may cause additional problems.

How much does it cost to fix P1594?

Repair costs for P1594 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect and repair Automatic Transmission Diagnosis Input Signal wiring and connectors
🔧 Replace faulty Automatic Transmission Diagnosis Input Signal

1
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2
Check for recalls
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3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.