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Engine Control Module (ECM)
This photo shows the same type of part you'll receive. Since each used part has its own wear and scratches, yours may look slightly different. Check the product notes for details about the condition of this specific part.

2003 - 2005 BMW Z4 Engine Control Unit (ECU) (OEM)

Only 1 left in stock
$78.95

ℹ️ Product Notes

This is a used part. It is the main computer module that controls your engine (ECU/ECM).

This computer must be programmed to your car's VIN by a mechanic. Match your old part number exactly before buying.

Original Part #(s): 12147529787, 12147533361, 7533361
Condition: Excellent (A)
Like new, minimal to no wear
160,000 miles
Odometer reading when part was removed
See Other BMW Z4 Engine Control Module (ECM)s
SKU #
7700881-36895-095

Why Buy Used OEM Parts?

✓ Quality-Verified: Every used OEM part we sell has been professionally inspected and tested to ensure it meets our quality standards. While it may show some cosmetic wear from previous use, it's fully functional and ready to install.

✓ Original Equipment: This is a genuine OEM (Original Equipment Manufacturer) part - the exact same part that came with your vehicle from the factory. It's designed specifically for your make and model, ensuring perfect fitment and performance.

✓ Works Like New: Despite some visual wear, this part will perform just as well as a brand new one. The internal components and functionality are intact, giving you the same reliability you'd expect from OEM quality.

✓ Significant Savings: Save 50-80% compared to buying new! Used OEM parts offer exceptional value - you get factory quality at a fraction of the cost. It's the smart choice for budget-conscious vehicle owners who won't compromise on quality.

✓ Risk-Free Purchase: We stand behind our used parts with a generous 6-month warranty, 30-day returns, and 100% money-back guarantee. If it doesn't work out for any reason, simply return it for a full refund. You have nothing to lose!

🛡️ 30-Day Returns + 6-Month Warranty - Buy with Confidence!

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Vehicle Fitment Guide

This part fits the following vehicles:

BMW
Z4 2003-2005 (tapclick to expand)(tapclick to hide)
Swipe left/right to see more info
SubmodelSUB-
MODEL		 Body Style Years Engine Attributes
2.5i Convertible 2003 - 2005 L6 2.5L RWD | Automatic & Manual | Fits 2.5L or 3.0L M54 engine models
3.0i Convertible 2003 - 2005 L6 3.0L RWD | Automatic & Manual | Fits 2.5L or 3.0L M54 engine models
2004

⚠️ Important: Please verify your vehicle's year, make, model, and specifications before ordering. If you're unsure about fitment, contact our customer service team for assistance.

Policies

Shipping & Handling

  • Standard shipping: 3-7 business days via UPS Ground
  • Parts are carefully packaged to prevent damage during transit

Returns (30 Days)

We accept returns within 30 days of delivery for this part.

  • Defective parts: We will replace the part or issue a refund at our discretion
  • Electronic parts: Must be returned with the sealed inspection bag unopened. The clear bag allows full visual inspection before opening. Once opened, electronic parts can only be exchanged for a replacement if defective — no refunds
  • Programming: "Needs to be programmed to my vehicle" is not a valid return reason. Many modules require dealer programming — we're happy to help connect you with resources if your dealer says it's not programmable
  • Return shipping: We cover return shipping as part of our 100% money-back guarantee
  • Parts must be returned in original packaging and unmodified condition
  • Poorly packaged returns that arrive damaged will not be credited

6-Month Warranty

All used parts include a 6-month warranty from the date of purchase.

  • If your part fails within 6 months, we will send a replacement
  • Refunds are only issued if we cannot provide a suitable replacement
  • Warranty covers defects — not installation errors, misuse, or damage after installation

Note: Warranty is for replacement, not refund. A part failing on day 80? We'll replace it. But the return window for refunds is 30 days.

Damaged in Shipping?

If your part arrives damaged:

  • Stop immediately — do not install the part
  • Keep all original packaging and boxes
  • Take clear photos of the damage and packaging
  • Contact us within 48 hours of delivery

We will handle the carrier claim. You are not responsible for shipping damage — we just need your help documenting it.

Order Cancellation

Orders can be cancelled before shipment for a full refund. Once shipped, cancellations follow our return policy.

Symptoms & Diagnosis

Warning Signs the Engine Control Unit (ECU) is Failing

  • Check Engine Light is on and won't go off
  • Engine misfires or runs rough
  • Poor fuel economy
  • Difficulty starting the engine
  • Stalling or dying unexpectedly
  • Transmission shifting problems
  • Complete engine failure

How to Test if This Part is the Problem vs Other Components

Testing an ECU requires specialized equipment and knowledge. A mechanic will typically:

  1. Check for Diagnostic Trouble Codes (DTCs): Using a scan tool to read codes stored in the ECU.
  2. Inspect Wiring and Connections: Looking for damaged or corroded wires and connectors.
  3. Test Sensors and Actuators: Verifying that sensors are sending correct signals to the ECU and that actuators are responding properly.
  4. Perform Voltage and Ground Tests: Ensuring the ECU is receiving proper power and ground.
  5. Substitute a Known Good ECU (if available): This is the most definitive test, but it's not always possible.

Common Failure Causes for This Part

  • Overheating due to engine heat
  • Water damage from leaks or flooding
  • Electrical surges or short circuits
  • Physical damage from accidents
  • Age and normal wear and tear

Buyer's Checklist

What to Look for When Buying This Part

  • Correct Part for Your Vehicle: Make sure the part is specifically designed for your 2002-2005 BMW 745i or 745Li.
  • Condition: Consider whether you want a used OEM or a new aftermarket part.
  • Warranty: Check if the part comes with a warranty.
  • Seller Reputation: Buy from a reputable seller with good reviews.

Quality Indicators for the Available Options

FeatureUsed OEMNew Aftermarket
OriginOriginal part from the vehicle manufacturerMade by a third-party manufacturer
TestingTypically tested before resaleNew, but may not have been tested as thoroughly
PriceGenerally lower than new aftermarketGenerally higher than used OEM
ReliabilityCan be very reliable if properly inspectedReliability can vary by manufacturer

What's Typically Included with the Part

  • The Engine Control Unit (ECU) itself.
  • Sometimes, installation instructions (though these are often generic).

Installation Overview

Difficulty Level and Estimated Time

  • Difficulty: Medium to High
  • Estimated Time: 1-3 hours

Special Tools Needed (If Any)

  • Basic hand tools (sockets, wrenches, screwdrivers)
  • Scan tool to read and clear diagnostic trouble codes
  • Possibly a multimeter for electrical testing

Critical Steps and Tips

  1. Disconnect the battery: This is crucial to prevent electrical damage.
  2. Locate the ECU: Usually under the hood or inside the passenger compartment. Consult your vehicle's repair manual.
  3. Disconnect the wiring harness: Be careful not to damage the connectors.
  4. Remove the old ECU: Unbolt or unclip it from its mounting bracket.
  5. Install the new ECU: Reconnect the wiring harness and bolt it in place.
  6. Reconnect the battery:
  7. Program the ECU (if required): Some ECUs need to be programmed to your vehicle's specific settings. This often requires a specialized scan tool.
  8. Clear any diagnostic trouble codes.

Whether DIY is Recommended or Professional Installation is Better

  • Professional installation is highly recommended, especially if the ECU needs to be programmed. Incorrect installation or programming can damage the ECU or your vehicle.

Buying Options

Compare: Used OEM, New Aftermarket

When replacing your Engine Control Unit, you have two main choices: used OEM and new aftermarket. Each has its own benefits.

Used OEM: Best Value

Used OEM ECUs are original parts that came from the factory. They offer:

  • Genuine Factory Parts: Made to the exact specifications of your vehicle.
  • Tested and Inspected: Typically tested to ensure they are working properly.
  • Significant Cost Savings: Usually much cheaper than new parts.

New Aftermarket

New aftermarket ECUs are made by third-party manufacturers. They offer:

  • Brand New: Never been used before.
  • Built to OE Specs: Designed to meet or exceed the original equipment specifications.

Typical Lifespan

How Long This Part Normally Lasts

  • An ECU can last for the entire lifespan of the vehicle, often 10-15 years or more.

Factors That Affect Longevity

  • Operating Temperature: Extreme heat can shorten the lifespan of the ECU.
  • Electrical Surges: Power surges can damage the sensitive electronics inside the ECU.
  • Moisture: Water damage can cause corrosion and short circuits.
  • Vibrations: Constant vibrations can loosen connections and damage components.

Price Ranges

Budget vs Mid-Range vs Premium Options

  • Used OEM: $150 - $400
  • New Aftermarket: $300 - $700

Labor Cost Considerations if Applicable

  • Professional installation: $100 - $300 (depending on the shop and complexity of the job)
  • Programming (if required): $50 - $200

Total Job Cost Estimates

  • Used OEM + Installation: $250 - $700
  • New Aftermarket + Installation: $400 - $1000

Vehicle-Specific Notes

Known Issues for This Vehicle's System Related to This Part

  • The 2002-2005 BMW 745i and 745Li are known for electrical issues, which can sometimes affect the ECU.
  • Water leaks into the electronics box can damage the ECU.

Any TSBs or Common Complaints

  • Check with a trusted mechanic or online resources for any Technical Service Bulletins (TSBs) related to ECU issues in these models.

Verification After Install

How to Confirm Proper Operation

  • Start the engine and let it idle for a few minutes.
  • Check for any warning lights on the dashboard.
  • Take the vehicle for a test drive to see if it runs smoothly and shifts properly.
  • Use a scan tool to check for any new diagnostic trouble codes.

What to Look/Listen for to Verify It's Working Correctly

  • Smooth engine operation
  • Proper shifting
  • No unusual noises
  • No warning lights on the dashboard
  • Normal fuel economy

FAQ

Q: Will this ECU need to be programmed to my car?
A: Possibly. Some ECUs require programming to match your vehicle's specific settings. Check with a mechanic or the seller to confirm.

Q: How do I know if my ECU is really the problem?
A: It's best to have a qualified mechanic diagnose the issue. They can perform tests to rule out other potential causes.

Q: What happens if I install the ECU incorrectly?
A: Incorrect installation can damage the ECU or your vehicle's electrical system. It's recommended to have it installed by a professional.

Q: Do used ECUs come with a warranty?
A: Some sellers offer warranties on used ECUs, but it varies. Check the seller's terms and conditions before buying.

Q: Can I return the ECU if it doesn't fix my problem?
A: Check the seller's return policy before buying. Some sellers offer returns, but others don't.

Part Specifications

OEM Part Numbers:

  • BMW: 12147529787, 12147533361, 7533361

Fits Years: 2003 2004 2005

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