P0899 — Transmission Control System MIL Request Circuit High

What Does P0899 Mean?

P0899 is a diagnostic trouble code indicating: Transmission Control System MIL Request Circuit High. This code relates to the transmission system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P0899

⚠️ Check Engine Light (MIL) illuminated
⚠️ Transmission Control System MIL Request reading stuck at maximum value
⚠️ Related system operating erratically or in default mode
⚠️ Harsh or delayed shifting

Common Causes

🔍 Short to voltage in Transmission Control System MIL Request wiring harness
🔍 Corroded or water-damaged Transmission Control System MIL Request connector
🔍 Faulty Transmission Control System MIL Request outputting maximum voltage
🔍 Damaged wiring rubbing against metal components
🔍 ECM/PCM internal fault (rare)

Frequently Asked Questions

What does P0899 mean?

P0899 indicates: Transmission Control System MIL Request Circuit High. The vehicle's computer has detected that the Transmission Control System MIL Request is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P0899?

Only short distances if absolutely necessary. P0899 affects a critical system and should be diagnosed within a few days to avoid further damage.

How much does it cost to fix P0899?

Repair costs for P0899 typically range from $20 to $500, 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 Transmission Control System MIL Request wiring for short to voltage
🔧 Clean or replace corroded Transmission Control System MIL Request connector
🔧 Replace faulty Transmission Control System MIL Request

1
Find your vehicle above
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P0899: Transmission Control System MIL Request Circuit High