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

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

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.

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.