Trying to determine if I have a bad ECM; 98 Cobra

[b4unoit]

I have a 1998 Cobra. It only has 43K miles, it's a weekend cruiser. Last time I drove it for 30 minutes and parked it. Came back a few minutes later, no start. I realized the fuel pump had locked up. Replaced it and the maxi fuse that blew when the pump seized.

I have no power to the pump. I have good ground at pump. Naturally, I assumed it took out the CCRM, replaced it with a new one, no change. I have checked all powers and grounds in and out of the ECM and CCRM. Pin 5 is dead out of CCRM. While I was checking all this I grounded pin 18 on the CCRM and the pump starts working.

Have I cooked the ECM or is there another possible explanation? Is there is anything else to check? I'd like to exhaust all possibilities before spending the money on new ECM, progamming etc...

Thanks!

 

[Noobz347]

Have you tried pulling codes?

 

[b4unoit]

P0230 Fuel Pump Primary Circuit Malfunction

 

[Noobz347]

P0230 – Fuel Pump Primary Circuit (1998 Mustang Cobra)


This code means the computer tried to turn on the fuel pump relay, but the circuit didn’t look right. Here’s how to track it down step by step.

Tools Needed​

• Test light (cheap at any auto parts store)
• Volt meter (DVOM, digital or analog)

Step 1 – Check the Fuses First​

• Under-hood fuse box (Power Distribution Box):
  
  • Fuse #14 (20A, yellow) = Fuel pump power
  • Fuse #18 (20A, yellow) = PCM power relay feed
• In-car fuse panel (driver’s kick panel):
  
  • Fuse #8 (20A, yellow) = PCM relay & fuel system

Replace any blown fuse. If they blow again → shorted wire or bad relay.

Step 2 – Find the Fuel Pump Relay​

• On a ’98 Cobra, the fuel pump relay lives inside a black box called the CCRM (Constant Control Relay Module).
• Location: Passenger side fender well, in front of the tire, behind the plastic splash shield.

Step 3 – Relay Basics (Wire Colors)​

• Red (RD) = Battery power in (should be 12V all the time).
• Dark Green/Yellow (DG/YL) = Computer control (PCM grounds this to turn relay on).
• Red/Black (RD/BK) = Power out to fuel pump.
• Black (BK) = Ground.

Step 4 – Quick Checks​

1. Key ON (don’t start). Listen at the fuel tank — pump should buzz for ~2 seconds.
2. No buzz? Use test light/meter at the pump connector above the tank:
   
   • DG/YL wire = power feed (should get 12V for 2 sec at key-on).
   • Black wire = ground.
   • If you get power and ground but pump doesn’t run → bad pump.
   • If no power → problem is relay/CCRM, wiring, or PCM control.

Step 5 – PCM Command Check​

• Back at the CCRM:
  
  • Clip test light between battery + and DG/YL wire.
  • Turn key ON. Light should blink ON for 2 sec → PCM is trying to ground the relay.
  • If it never lights → PCM driver issue or wiring break.

Step 6 – Relay Output Check​

• Still at CCRM:
  
  • With key ON, RD/BK wire should show +12V for 2 sec.
  • If PCM is commanding (Step 5 worked) but no 12V here → bad relay inside CCRM. Replace CCRM.

Logic Diagnostics​

• Blown fuse → fix fuse/short.
• No PCM command → wiring or PCM problem.
• PCM commands but relay dead → replace CCRM.
• Relay sends power but pump doesn’t run → bad pump or ground.

Quick and Dirty:

1. Check fuses first (#14, #18 under hood; #8 inside car).
2. Listen for pump prime.
3. If no prime, check for power at the pump.
4. Work backwards: pump → wiring → relay (CCRM) → PCM.

Let us know what you find!

 

[b4unoit]

Wow! That's really helpful. I'll do this battery of tests and report back.
Thanks!

 

[b4unoit]

I haven't had a chance to run the tests. I'll post results when I do.

 

[b4unoit]

Ran all the tests you recommended. Had to come to the conclusion the ECM is bad. Everything checks out. All fuses and relays are good. It just won't ground pin 18 out of CCRM. I can't trigger the fuel pump with the scanner either. I'll replace ECM, if it doesn't fix the problem I'll repost. Thanks for the help!