DME Control Unit Chip Installation – 2.5L NA

Overview

This procedure outlines the steps to replace the chip in the DME (Digital Motor Electronics) control unit of a Porsche 944 with an 8-valve engine. The DME chip controls engine parameters, and replacing it can optimize performance. This guide is specific to the pre-1985.5 (83-85.5) and 1985.5 onwards (86-88) models, ensuring safe and accurate chip installation to avoid damage to the control unit.

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Tools Required

• Phillips screwdriver
• Straight tip screwdriver (small)
• 7mm (9/32 inch) wrench or 7mm (9/32 inch) socket and ratchet
• Grounding strap (optional, recommended for dry or static-prone environments)

Parts Required

• Replacement DME chip, 944 618 111 00 (verify compatibility with your model year)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• DME Control Unit Removal
• DME Control Unit Installation

Step-by-Step Procedure

Step 1: Remove the DME Control Unit

1. Follow this link to ensure this step – DME Control Unit Removal – is followed accurately to remove the DME control unit from the vehicle.
2. Before detaching the control unit from its mounting bracket, note its orientation. Sketch a diagram of how it is mounted to ensure correct reassembly.
3. Using a 7mm (9/32 inch) wrench or socket and ratchet, remove the control unit from the mounting bracket.

Step 2: Prepare the Work Area

4. Place the DME control unit on a clean, dry, flat surface to prevent damage.
5. If working in a dry or static-prone environment, wear a grounding strap to protect the unit from static electricity.

Step 3: Open the DME Control Unit

6. Turn the control unit so the back side (opposite the electrical connector) faces up.
7. Using a small straight tip screwdriver, gently pry up the casing tabs on the rear of the module.
8. Once all tabs are raised, slide the module cover off to access the internal circuit boards.

Step 4: Separate the Circuit Boards

9. Locate the two printed circuit boards inside, mounted face-to-face and separated by plastic posts. The boards are connected by a ribbon cable at one end.
10. Identify the plastic posts holding the boards together. Each post is split in the middle and may have a central pin.
11. Insert a small straight tip screwdriver into the slit at the middle of each post. Gently pry back and forth to separate the two halves. If a pin is present, remove it first.
12. Once all posts are separated, lift the top circuit board on the ribbon cable side, then slide it toward the ribbon cable to disengage it from the electrical connector.
13. Lay the circuit boards flat, keeping the ribbon cable intact, to access the chip.

Step 5: Replace the DME Chip

14. Locate the DME chip on the circuit board:For Pre-85.5 models:– The chip is a 24-pin chip, typically inserted into a socket connector but may be soldered in some cases. If soldered, professional desoldering equipment is required, and this guide assumes a socketed chip.

    For 85.5 Onwards models:

    – The chip is a 24-pin chip, inserted into a socket connector, and should be the only chip not soldered in place.

15. Note the chip’s orientation before removal. Look for an indent or notch on one end of the chip and socket, which must align during installation.
16. To remove the chip, slide a small straight tip screwdriver under one end and gently pry up. Alternate between both ends, prying gently, until the chip is fully removed. Avoid excessive force to prevent damage to the socket.
17. Align the new DME chip, 944 618 111 00, with the socket, ensuring the indent on the chip matches the indent on the socket.
18. Gently press the chip into the socket, ensuring all pins are seated correctly. Press down on the center until it is fully inserted.

Step 6: Reassemble the DME Control Unit

19. Fold the circuit boards back together, aligning the top board with the slot on the electrical connector.
20. Align the plastic posts on both boards and gently press to snap them together.
21. Slide the module cover back onto the control unit and bend the tabs to secure it in place.

Step 7: Reinstall the DME Control Unit

22. Mount the control unit back onto the mounting bracket, referring to your sketch for correct orientation.
23. Reattach the electrical connector to the control unit.
24. Follow this link to ensure this step – DME Control Unit Installation – is followed accurately to reinstall the control unit in the vehicle.

Post Procedure Checklist

• Verify that the DME control unit is securely mounted and the electrical connector is firmly attached.
• Start the engine and check for proper operation, ensuring no warning lights appear on the dashboard.
• Drive the vehicle for 5 miles (8 km) to confirm the new chip functions correctly under normal conditions.
• Inspect the DME control unit for any signs of loose connections or damage after the test drive.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube