Jump to content

GrandBoost98s Comanche 2


Recommended Posts

Both 2.5L & 4.0L use a B+Latch relay, thanks for pointing that out. When you get a chance, can you do some preliminary voltage checks?

 

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage (B+) on the following pins (use battery_negative terminal for ground):
D1_2:  B+ (Hot during KEY ON/CRANK).
D1_5:  B+ (Hot at all times)
D1_6:  At KEY ON (B+ (Hot for 2-3 seconds)) or CRANKING (B+ (Hot during CRANK)).
 

D1_D2.jpg.6a80c3f7836373dcaeefc968569a8d65.jpg

 

 

With KEY ON, measure for voltage at D2-4. Determine if flipping the KILL SW changes the voltage reading on that pin.

Link to comment
Share on other sites

  • Replies 149
  • Created
  • Last Reply

Top Posters In This Topic

11 hours ago, Ωhm said:

Both 2.5L & 4.0L use a B+Latch relay, thanks for pointing that out. When you get a chance, can you do some preliminary voltage checks?

 

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage (B+) on the following pins (use battery_negative terminal for ground):
D1_2:  B+ (Hot during KEY ON/CRANK).
D1_5:  B+ (Hot at all times)
D1_6:  At KEY ON (B+ (Hot for 2-3 seconds)) or CRANKING (B+ (Hot during CRANK)).
 

D1_D2.jpg.6a80c3f7836373dcaeefc968569a8d65.jpg

 

 

With KEY ON, measure for voltage at D2-4. Determine if flipping the KILL SW changes the voltage reading on that pin.

Absolutely! I will do that as soon as I get home from work. I appreciate you taking the time to help me with this :beerchug: 


Last night I took it easy, was hot and humid. Noticed the tail lights were thrown on with whatever they had laying around. The driver side only had one screw holding it on and the passenger side had three deck screws in it! So I went through my tub of jeep hardware and found some proper screws to install

Link to comment
Share on other sites

20 hours ago, Ωhm said:

Both 2.5L & 4.0L use a B+Latch relay, thanks for pointing that out. When you get a chance, can you do some preliminary voltage checks?

 

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage (B+) on the following pins (use battery_negative terminal for ground):
D1_2:  B+ (Hot during KEY ON/CRANK).
D1_5:  B+ (Hot at all times)
D1_6:  At KEY ON (B+ (Hot for 2-3 seconds)) or CRANKING (B+ (Hot during CRANK)).
 

D1_D2.jpg.6a80c3f7836373dcaeefc968569a8d65.jpg

 

 

With KEY ON, measure for voltage at D2-4. Determine if flipping the KILL SW changes the voltage reading on that pin.

 

Using your preferred test light. All of those check out good. And yes, the kill switch made the light go out. I also tested for voltage on D2_4. Key on it has 12.08v and when I turn the kill switch off I get 1.82v

Link to comment
Share on other sites

5 minutes ago, Ωhm said:

D1_2, D1_5 & D1_6 testing are all good readings. D2_4 testing shows that we're dealing with the B+Latch Relay. Why? IDK. Let me look for my next question.

For what it's worth, I noticed the shift indicator flash and was able to hear the fuel pump prime when turning the toggle switch back on

Link to comment
Share on other sites

7 minutes ago, GrandBoost98 said:

For what it's worth, I noticed the shift indicator flash and was able to hear the fuel pump prime when turning the toggle switch back on

 

Somehow, I think the toggle SW shuts down the ECU. Anyone else got a understanding for the B+Latch Relay circuit. It's a strange circuit.

Link to comment
Share on other sites

1 hour ago, Ωhm said:

Determine which Relay is the B+Latch Relay. Check for HOT AT ALL TIMES on PIN_1 (RED). PIN_4 & PIN_5 should have PINK wires. Pink should help with relay ID. 

 

597754326_C215BplusRelay.jpg.9d03978a02c8bd5bb05318ba9220dc4f.jpg

Pin 1 hot key on or off. And the toggle switch made no difference 

Link to comment
Share on other sites

17 minutes ago, Ωhm said:

Turn KILL SW OFF. Remove B+Latch relay. Jumper wire between PIN_1 and PIN_4. See if engine STARTS and RUNS.

 

Kill switch off. B+ relay removed and pins 1 and 4 jumped. It started up and ran for a couple mins and I revved it up a few times. Should I run it longer or is that good?

 

What really surprised me is that doing this "fixed" the two crank start! I was able to start it on the first crank 3 times. So then I removed the jumper wire, reinstalled the relay, turned on the kill switch and it went back to two crank starts

Link to comment
Share on other sites

6 minutes ago, GrandBoost98 said:

Kill switch off. B+ relay removed and pins 1 and 4 jumped. It started up and ran for a couple mins and I revved it up a few times. Should I run it longer or is that good?

That's good. Proves we don't need the kill switch.

 

Next question is "will ENGINE START and RUN with KILL SW OFF and B+Latch Relay reinstalled?

Link to comment
Share on other sites

1 minute ago, GrandBoost98 said:

No, does not start just cranks

 

I think having the KILL SW answered my own question and that proved it. Do you have a known good relay? Swap them out, Try START and RUN again. I'm thinking faulty relay, relay (Coil) ON circuit or ECU not controlling B+Latch Relay function.

 

Link to comment
Share on other sites

12 minutes ago, Ωhm said:

 

I think having the KILL SW answered my own question and that proved it. Do you have a known good relay? Swap them out, Try START and RUN again. I'm thinking faulty relay, relay (Coil) ON circuit or ECU not controlling B+Latch Relay function.

 

 

I have a drawer of used relays and fuses. I tried 3 different relays and they all acted the same. No start with kill switch off. I did notice that I can turn the kill switch off after it starts running and it will continue running

Link to comment
Share on other sites

KEY OFF. KILL SW OFF. Remove Relay. Continuity test

between D2_2 and B+Latch Relay PIN_2

between D2_4 and B+Latch Relay PIN_5

between D2_4 and B+Latch Relay PIN_4

 

Looking for 0_Ωs.

Link to comment
Share on other sites

7 minutes ago, Ωhm said:

KEY OFF. KILL SW OFF. Remove Relay. Continuity test

between D2_2 and B+Latch Relay PIN_2

between D2_4 and B+Latch Relay PIN_5

between D2_4 and B+Latch Relay PIN_4

 

Looking for 0 Ωs.

D2-2 to pin 2 =4.3ohms

 

D2-4 to pin 5 =1.5ohms

 

D2-4 to pin 4 =1.5ohms

Link to comment
Share on other sites

I'm calling that as circuits are NOT open. Next two tests involve the ECU connector. Looking for continuity. Same conditions KEY OFF. KILL SW OFF.

 

D2_2 and C200_7

D2_4 and C200_19

 

If both test good, all wiring test good. Suspect ECU.

 

957049564_C200ECU2_5L.jpg.3019c8507cfe3037fd93120e846191f2.jpg

 

Link to comment
Share on other sites

@Ωhm

Ugh, I just had that out too lol

 

Had to rig up an extention. That by itself ohmed out at 1.4ohms

 

D2-2 c200-7 =4.2ohms

D2-4 c200-19= 1.5 ohms

 

So you're saying a new ECU would fix all my problems? This would give power from pins 1 to 4 on the B+ relay and I could eliminate the kill switch and related wiring? Which in turn would fix my two crank start as well? 

 

If so, do I need a specific 2.5l ECU or is one from any mj/xj okay? 

 

Screenshot_20230718_204840_Gallery.jpg

Link to comment
Share on other sites

13 minutes ago, GrandBoost98 said:

So you're saying a new ECU would fix all my problems?

 

I'm not saying, I'm hoping.

 

 

13 minutes ago, GrandBoost98 said:

This would give power from pins 1 to 4 on the B+ relay and I could eliminate the kill switch and related wiring?

 

If B+Latch Relay worked properly (relay jumper test) you should be able to get rid of kill switch.

 

13 minutes ago, GrandBoost98 said:

If so, do I need a specific 2.5l ECU or is one from any mj/xj okay? 

 

@eaglescout526  ECU request help here. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share


×
×
  • Create New...