Retrofit D2/P38 Cruise Control ECU
 

How to: Retrofit a D2/P38 Cruise Control ECU into your D1

Below is our stock cruise control ECU. They're unreliable and fail often.
Attachment 14539

This is a D2/P38 cruise control ECU with pigtail. They're cheap, abundant, and much more reliable.
Attachment 14540

Extract the guts.
Attachment 14541

Cut off the connector. I used a rotary cut off tool.
Attachment 14542

Solder the pigtail to the connector using the information below. Then insulate it. I used liquid electrical tape.
Attachment 14543

Now you have this:
Attachment 14544

Reinstall. It fits perfectly in the stock location.
Attachment 14545


Selecting a D2/P38 cruise control ECU:

There are several different "tunes" for the D2/P38 cruise control ECUs, depending on engine size (4.0 vs 4.6). If you have a stock 3.9 or 4.0 engine, make sure you get an ECU from a 4.0 D2/P38 for smoothest operation. A 4.6 ECU will work fine, but with less smooth operation.

Of course, also make sure it includes the pigtail so you can make an adapter. Our common used LR parts suppliers can supply this upon request.


Pinouts:

D2 and P38 cruise control ECU's use the same pinout but with different pigtail wire colors. Use this pinout information to match you old D1 ECU's connector pins to the new ECU's pigtail depending which it came from.

D1 cruise control ECU (AMR 1173):
Pin 1: Orange/Blue - Actuator Pump Power
Pin 2: Not Used
Pin 3: Grey/Yellow - Set Button (from inverter)
Pin 4: Red/Yellow - Resume Button (from inverter)
Pin 5: Green/Purple - Brake Light Switch
Pin 6: Orange/Pink - Actuator Valve Control
Pin 7: Orange/Red - Actuator Pump Control (thicker gauge)
Pin 8: Black - Earth or Ground
Pin 9: Orange/Red - Brake Pedal Vent Switch (thinner gauge)
Pin 10: Orange/White - ECU Power +
Pin 11: Yellow - Speed Signal
There are two wires with the same color-code of Orange/Red but one is thicker than the other as noted above

99+ P38 cruise control ECU (AMR 5700):
Pin 1: Orange/Red - Brake Pedal Vent Switch
Pin 2: Red/Yellow - Resume Button
Pin 3: Not Used
Pin 4: Grey/Yellow - Set Button
Pin 5: Green/Purple - Brake Light Switch
Pin 6: Not Used
Pin 7: Orange/Red - Actuator Pump Control
Pin 8: Orange/White - ECU Power +
Pin 9: Not Used
Pin 10: Not Used
Pin 11: Orange/Blue - Actuator Pump Power
Pin 12: Not Used
Pin 13: Not Used
Pin 14: Not Used
Pin 15: Yellow - Speed Signal
Pin 16: Pink/Red -Diagnostic Line (Unnecessary for conversion to GEMS)
Pin 17: Orange/Pink - Actuator Valve Control
Pin 18: Black - Earth or Ground

D2 cruise control ECU (AMR 5700)(Uses 11 wires):
Pin 1: Purple/Green - Brake Pedal Vent Switch
Pin 2: Blue/White - Resume Button
Pin 3: Not Used
Pin 4: Red/White - Set Button
Pin 5: Green/Grey - Brake Light Switch
Pin 6: Not Used
Pin 7: Black/Red - Actuator Pump Control
Pin 8: White/Yellow - ECU Power +
Pin 9: Not Used
Pin 10: Not Used
Pin 11: White/Blue - Actuator Pump Power
Pin 12: Not Used
Pin 13: Not Used
Pin 14: Not Used
Pin 15: Pink/Green - Speed Signal
Pin 16: Pink - Diagnostic Line (Unnecessary for conversion to GEMS)
Pin 17: Black/Yellow - Actuator Valve Control
Pin 18: Black - Earth or Ground

Have you tested and this works?

Yes, works great.

What was wrong with yours?
Not working at all?
Mine wont hold speed anymore, set it and the truck starts slowing down at the first hill or headwind.
Speeds back up going down hill.

As testimony to the reliability of the DII/P38a cruise control ECU, I have over two dozen on hand. If anyone else wants to try Eric's mod, I have plenty of 4.0 ECU's with pig tails for just $17.50 including shipping.

I first fixed my cruise control a while ago. I fixed the vacuum hoses, clogged vacuum pump, and brake switch but still couldn't get it to work. I then tested each pin of the CC ECU for the correct signal, resistance, or voltage. The inputs all appeared to be working correctly, and I had tested the pump, so it had to be the ECU. I replaced the ECU, but it was also bad. So I replaced it again with another used one and it finally worked, but then that one stopped working. So I started looking for a better solution.

Got it, thank you.
I'm tearing into mine in the spring, for now just no cruise.

Thank you for the post on how to do this, it is good to know that an alternative to the unreliable $50 AMR1173. As of about 5 minutes ago, I am attempting to get in touch with Paul Grant above to see if he has any more of those units with the pigtails for my 95 LWB. If he doesnt, does anyone here know another reliable source for the AMR5700 and the pigtail?
Thanks all!

I have plenty of these ECU's. They're $17.50 shipped with pigtails. You can PayPal me using any of the email addresses in my signature or call Monday with a credit card.