Where is the location of the pulse module, and what does it do!! Thanks for the help!!!

 

It is located in the under hood fuse panel closest to the outside.
It senses the key being turned to start and takes over from there, timing how long to run the starter motor, and also removing power from the starter when the engine reaches a certain RPM.

 

Exactly, think of the pulse module as an "AND" gate. If the key is turned to "start" AND the ECM is sending an enable to the pulse module, the pulse module powers the starter.

Iin automatic-equipped cars:

• The pulse module engages the starter anytime there is an enable from the ECM and the key is turned to "start", but the key's input is 'latched", that is, once there is a "start" from the key, even if the 'start' goes away from the key, the pulse module keeps the starter engaged.
• When the engine rpm gets to 400 rpm, the enable from the ECM goes away, disabling the pulse module's starter output.

In manual-equipped cars:

• The pulse module engages the starter anytime there is an enable from the ECM and the key is at "start", but it does not latch the key condition, if you release the key, the pulse module disengages the starter right away.
• When the engine gets to 400 rpm, the enable from the ECM goes away, disabling the pulse module's starter output.

At least, that is how I THOUGHT it worked. But a close look at the student reference implies that the ECM has the "AND" gate, not the pulse module:


This implies that the pulse module in a manual car is nothing more than a jumper wire.
Since I own a manual-equipped car, I now want to know for sure.

With temperatures in the upper 90's here today, Im not sure how much I want to verify this today. But the ORIGINAL student manual is vauge, is the switch contact shown the "START" or "ON" contact? Below is the manuals' diagram, above is my interpretation of same.


As is always the case, the documentation for the car is not always accurate and is never complete.

 

Well, I took mine apart. The Manual car has two relays. The relay on the right is not used, as there is

nothing plugged into the connector the contains that relay's "low side" coil pin.


The other relay's normally open contact feeds the wire going to the starter/solenoid.

I don't see any way that an "AND" gate exists on this board.


So all of the gating is done in the ECU, at least in the manuals. I'd like to see the PM out of an automatic, and I will when I visit Vickie here soon....

 

Mark - here is a picture of the automatic pulse module that you were looking for. It's out of my SRT with notes of how I think it should respond under certain conditions. I am having the "No Crank" condition. After the condition started, I had the RCM rebuilt by DJ and put a new battery in on 8/16/2019 (mine tested bad under heavy load). Still not getting any cranking. I am looking at your theory that the PTCM will give the "go" or "no go" to the PM to get the car started. I haven't dug into the PTCM yet but I did make sure I was getting voltage to certain pins on it and contiuity between it and the PM on common wires. As far as I can tell, everything is getting voltage and ohming out like it should if I am reading the 8W-30-5 diagram correctly. With all that being correct, I am not getting 12VDC at F1 of the PM when the key is turned to start like I would expect. So, I took the PM without the case on it and hooked it back up to see if I could get the starter to turn by manually closing the relay and that works - the starter will crank ... but the car will not start. Everything is hooked up as it should be, key gets turned to the "START" and then released to the "RUN" position and I can close the relay but all it does is crank - doesn't even try to start. So, now I am wondering if the PTCM isn't giving the fuel/ignition commands for the car to run and that might be why I am not getting any voltage at F1? The PTCM isn't giving the command for that relay to close? That "SENSOR GROUND" at A2 of the PM and C4/35 of the PTCM has me baffled. I don't know what I am supposed to be checking at those two points but I did confirm the wire between them is good.

 

Did you ever resolve the "no crank" issue?
I am having the same issue, and have followed your troubleshooting to the extent above. Starting to think it is the PCM. Connected my autell code reader and indicates no faults (for what that's worth). Also looks like I have a high current draw when the car is off Key out. Had a noise coming from under the windshield cowl, and removed a horn/siren type of device. Do you know what that component is?
When attempting to starting the car also noticed the fuel pump does not come on for its aprox. 3 to 5 second cycle in the Run position before selecting Start. Believe this is also a PCM function. Running out of options on this, so any help appreciated

 

That is the famous-for-draining-batteries alarm siren. Many have replaced theirs, others just disconnected them and let it go at that.

TUrn key to START, if starter does not engage, release to ON.
Wait 45 seconds.
Does engine cooling fan warp up to high speed? If so, replace the RCM or send it to DJ for reworking.

If the engine fan does NOT warp up to high speed, we have other things to check. It is NEVER the PCM, avoid ANY garage that tells you the PCM is bad.

 

Mine turned out to be the SKREEM had gone bad. I wasn't getting the the common "3 tries then nothing" like what has been reported, but after banging my head against the wall for about a year, I took a chance and had the SKREEM deleted by Precision ECU out of Chicago. The guys over at the Mercedes Swap Shop (MSS) will caution you against having this done by Precision ECU and suggest you have it done by them. I had my car for about 2 years after the delete and never had any problems. I sold my car in March of 2023 and the new owners is using it as a daily driver and it is working great last I heard.

The item under the cowl is the alarm siren and it's best to get it out of there like you did, if not the entire unit, at least the battery. There is an updated unit you can install, but I think it's kind of pricey.

If your fuel pump is not running when you turn the key, have you checked the RCM? Getting it rebuilt by DJ Tighe was the best $50 I spent on the car. I believe the fuel pump relay is on the RCM - there are pictures on the forum of what each relay does. When you turn your key to on (not start), does your radiator fan spin up to a high RPM after about a minute of it being on (or sooner)?

 

Thanks to the both of you for replying. Up here in northern Ontario, I only see another crossfire occasionally, so local repair shops/dealer not an option. Actually, the closest dealer told me he wasn't authorized to sell them when they were available.
Full disclosure here; the fuel pump relay stopped working one day last year and left me on the side of the road. next day car ran fine for 3or 4 miles and quit again. Re soldered the cold solder joints and tried again with same results. Tried troubleshooting with voltmeter on the passenger seat hooked up to RCM pin E3 while driving and when the relay quit did not get the readings I was expecting. Believe the relay was intermittent, as much as I have never seen that condition before.
Let me source a brand new RCM (Amazon $122.00/ Rockauto $143.00) and then I can eliminate that component. Prefer this to rebuild.
I did the check regarding the cooling fan and it did not warp up to speed.
I will run the test again with new RCM.
Thanks again

 

I understand you wanting a new one, but for $50 DJ will replace all of the relays on the RCM and fix the solder joints. To this day, I have never heard someone say that DJ's repair had failed. But, if you do purchase a new one, you might still consider getting the original one rebuilt and keep it as a spare just in case. Are there any salvage lots around you that have a Crossfire in them that you could get the RCM out of? Might be worth a try. Also, I have seen DJ suggest to people to put a rubber band on the Fuel Pump relay to get them home when it fails while they are away from home. That could be another test for you to try to make sure it's the relay failing.

 

Yea, but I ordered a new one when mine crapped out, and sent my bad one to DJ. That way, got my car running in two days AND have a spare.

Best price I found:
https://www.autohausaz.com/pn/136364...kaAkVCEALw_wcB

 

OK pizzaguy, I am back with a rebuild RCM. Installed back in car and tried to start but no go. Traction control and engine control relays both pull in. Opened the pulse module and manually closed the start relay and the engine turned over with no fire even with fuel pump relay on manually.
I purchased the shop manual when I bought the car but looks like you have a higher level of documentation than I do.
What do you suggest as the next check point?
Thanks

 

I have only the 2005 SRT and 2007 Limited service manuals. GOt them both from this very site, in PDF form. My documents are not better, it's just that I've been leafing thru them, helping others, working on my three roadsters since 2009.

OK, you have the "myster no start" but in your case, the Engine Control relay pulls in. You know the starter and pulse module are OK. But do you KNOW the engine control relay is actually closing well enough to pass 12 volts for the ECU to start up? Here is a test:

Turn key to start, if it does not engage the starter, release to "ON".
Wait 45 seconds.
If the engine fan warps to high speed, your problem is no power from the RCM to ECU. You can find the problem with a voltmeter, either the RCM you have has a bad engine control relay (contacts bad) or the solder joint at the connector is fractured, the fuse on the RCM is blown or there is trouble in the harness.

If the engine fan does NOT run really fast, you have:
... a bad clutch interlock switch (manuals only)
... a bad shift lever assembly (autos only)
... a bad traction control relay on the RCM (or, again, fractured solder where the connector mates with the circuit board on the RCM).
... a defective ECU (never happens)
... a serious problem with the CAN BUS such that the Shift Lever Assembly (SLA) can't talk to the transmission control module (TCM) or between the TCM and ECU.

Make sure the fuses on the RCM are all good.

 

- Auto transmission
- no cooling fan rotation
- all fuses on RCM verified good
- Traction control output RCM plug C 4 &5 verified
- illumination mod fuse 4 (power for shift and trans mod) verified
am now determining what options I have for verifying CAN bus operation.
The start sequence, as I recall, when Key is in "on" the fuel pump will run for 2 seconds, but should only happen in park or neutral.( not happening on mine) Do any of the lights on the dash extinguish as the different mod come on line and report to the ECU.
On mine the TPMS lamp goes out,(discreet connection) and seatbelt lamp goes out. Can't remember if anything else changes or does the dash stay like that until engine start. Just trying to determine if the car is providing any clues on CAN bus health.
When shifter is moved from park to drive ,reverse it displayed up on the instrument cluster so believe that mod is good.
Think I will pull trans mod and verify power to board.
Currently looking at what options I have to check CAN bus
Thanks for the pointers

 

Do you know if any liquids was spilled on or into the shifter location?


.

 

Disconnect the cars battery for a minute, reconnect and try starting the car. Disconnecting will reset the anti-theft system; You will be starting with a clean slate.
Hopefully car will start. Then come back and tell us exactly how the car responds.
PS you need to have a good, well charged battery!

 

To Graphiteghost, no, there wasn't any fluid spilt on the shifter area. Car was stored indoors all winter, and started troubleshooting an intermittent fuel pump issue on RCM this spring when the no start issue appeared.
Not sure if I have caused the "no start" issue by cycling the ground connection on and off the battery during troubleshooting as occasionally I get a good size spark on connection, and this is with the key out of ignition, doors closed. Am thinking that I have caused a surge or something damaging a module.
Pizzaguy gave me a list of items to check, and working through them, the Transmission control module is where I spent a few hours troubleshooting yesterday, continuing today. The shift module is communicating with the instrument cluster so believe that is ok.
Transmission control mod troubleshooting has been a bit more challenging as the manual has some wrong info it it. Plug c206 and c207 where mixed up, and in troubleshooting the sci transmit voltage, Step #6, the procedure is to disconnect the plug C1 from module and check the voltage on the Data link connector.??? Course voltage will be zero. (unless I just messed up but I reviewed this) Jump to new thread I started "Data Link Connector"
To Zip439, Battery was disconnected overnight. Battery voltage at 12.8 volts connected to vehicle. Car did not start. (darn) The shift mod is not communicating with the instrument cluster now so will start looking into why that changed. The output from traction control relay Pin C4 and 5 is 12 volts. Power top looks good, heater fan runs, light work. Will update at end of the day.
Not giving up.

 

Just curios if you have tried this to be sure it isn't the starter?
To check if the starter is good open the Pulse Module and close the starter relay. Stater should turn on.

Also be sure your ground connections are clean and tight.

 

So you have a "no crank" and you are SURE the RCM is OK. Im not sure but you are.

So, the fan does not warp up to high speed when key is "ON", this means that, either the FCM and ECU are not powered up, OR that BOTH are successfully powered up.
Before going ANY farther, I'd verify that the FCM is powering up. There are two little wires on the FCM. Make sure the one in the MIDDLE of the module has battery voltage on it with the key ON.

IT MUST have BATTERY VOLTAGE on it with the key on for my "fan test" to be valid. If it has battery voltage with the key ON, then OK, we can proceed

In such a case, since you already verified the starter thru the pulse module (Zeracer missed that post), I'd ask you to verify that disconnecting the battery and reconnecting it does not give you 'three cranks and nothing'.
If yanking the battery cable off and putting it back on does not give you "three cranks and nothing", then we are back to what is probably an interlock issue somewhere. If you get three cranks and nothing, then we have a SKREEM issue, but I think we've been thru this (sorry, it's a long thread and I may be missing some details like Z did.)

Minor detail: The SLA talks to the TCM which then talks to the Instrument Panel. I agree that the SLA is probably OK, if it is telling the TCM that it is in Park, I would think the TCM would then tell the ECU that it's good to go.


JeffK in Greer, SC had a similar "no crank", let me contact him and see what the issue was.

 

Can you lock and unlock the doors with the FOB buttons? This relates back to the anti theft system.
And lets us know exactly what happened when you tried to start the car. You are missing details that are clues to what is going on. "Car did not start. (darn)" doesn't tell us anything.
Pizza guy also wants to know.
NOTED: " The shift mod is not communicating with the instrument cluster now ". This is new. you were in there yesterday and probably messed some connector up
Have you checked all the fuse under the hood and on top the RCM?
Who rebuilt the RCM?