Jeep ASD relay magic or not? Automatic Shut Down relay

The JEEP ASD “Automatic Shut Down relay”.

What is it, why is it there, how to does it work and why?
My engine stalls (shuts down) at anytime, or even cranking, why?
All comments are USA, not Export Jeeps.

Real JEEPS! ONLY! (all EFI cars have this, but is executed in different ways) EFI means Electronically Fuel Injected ( unlike mechanical injection)
On most cars the ASD is just software in the ECU/PCM. On jeeps its both, Software and Hardware, the ASD relay. (to me, they are all the same)

ASD relay “Automatic Shut Down relay” used on all EFI jeeps. 1990 to present.
What is it?
It is a safety device, that exists by LAW and for good reasons. It CAN prevent FUEL fires (the Classic Crash and burn reason) and engine hyrdolocking.

It does that by cutting fuel, spark and injection. (via hardware and software) (software means the PCM(ECU) instructions, in ROM “logic”)

It cuts fuel (and spark) if the PCM thinks, there is any danger of crash and burn.
The PCM drops the ASD relay for many reasons, this list is for all years. (some methods, are missing on early years) Any scan tool will show DTC errors for each failure cranking or running (SCAN it LOOK)

  1. Lost 12 volt DC electric power. (the ASD relay is dead with no power to it) dead as a door nail, as they say. (so,watch your dash voltmeter, or use a voltmeter at the CIG lighter power port) ( ASD relay Drops for “CAUSE”)
  2. Sees the spark weak or dead on the ignitor drive to Ignition coil primary pin. (it sees, and knows spark is bad here) (It can’t see the secondary High Voltage side, just the primary)
  3. Crank sensor bad. or misfiring. CKP
  4. Cam sensor bad, or misfiring, CMP.
  5. ASD input read back pin fails. (PCM commanded it but it refused to do its job) Shorted relay coil?
  6. Same ASD output read back. fails. PCM commanded it, but the relay is bad. dead output. (bad RELAY)
  7.  Immobilizer active. (failing or bad IMMO key, etc,) SKIM module is unhappy see dash light glowing telling you, SKIM failure. Any security failures, at all will glow the idiot lamps. The operators guide is clear there, read that. or hit home above and see SKIM
  8. On some newer years, the fuel pump relay output, is monitored and if it fails?, it sets DTC ERRORS, and drops the ASD. USE A SCAN TOOL! See WHY IT FAILED!

My OBD2 scan tool, can monitor, PCM 12volt DC power. (it has a unique PID for that) Pids are live data from sensors. Parameters IDs.

On even newer Jeeps with Throttle by wire, it might shut down with a catastrophic throttle by wire (TBW) T-body motor error or TPS stuck open on all cars, preventing “Toyota Run-Aways” if you get my drift. (lawsuits…)

FACT: In each case the PCM will log errors and show DTC errors, if you only LOOK! SCAN IT! With a REAL SCAN tool (buy/barrow/rented)
If you lost spark to all cylinders, not just 1, use this logic below:

  • ASD relay never closes? – Is a blown fuse and lost all power to the PCM.? The ASD must close for 2 seconds or its bad or the PCM is not closing it, ( PCM bad) or Bad ASD (coil inside open)
  • ASD relay closes for 2 seconds, only. – Is bad spark, bad CMP, bad CKP, scan it and crank at the same time
  • ASD relay closes for 2 seconds, but you discover no 12vdc at coil + or injector 12vdc power is dead (during said 2 seconds), or (0v) cranking. – This means the ASD relay is bad. (bad contacts, replace it)
  • ASD relay closes, but I have no spark to any cylinders. – So is bad Ignition coil, or crank /cam sensors or bad ignitor module. SCAN IT.
  • If the ASD relay drops driving and stalls the engine, or even parked idling, one of the above caused it. (older cars have, less checks) Stalls caused by ASD drop are in the 8 point list above.
  • Stalls caused by ASD not dropping first! Can be 50 causes, but in macro form is, bad engine bad spark plugs and wires, bad fueling, which can be flooding or lost fuel pressure (stavation)
  • Stalls for bad engine are lost compression hot. Some engine can do that, even stuck open head valves now or only HOT. (and many more issues inside the actual engine)
  • Stalls for spark are common, never tuning the car up every 60,000 miles (spark parts. etc)
  • For fueling issues are bad fuel, too much fuel (black spark tips) or starvation, finding this is easy, try to keep engine runing with hand sprayed test fuel.
  • Can you save the stall with A fast right foot action? Yes, then its not the ASD, causing stalls. Its fueling or other issues. (even a stuck closed ISC idle valve can stall any engine,hot,due to lack of air to idle engine!)

DO NOT work alone, get someone to start engine and you look at the ASD!

The system and how it works.
The ASD has engine startup logic that is unique to JEEPs. (in part)
You must crank with in seconds or the key on, is ignored by many jeeps. (the ole’ key off, key on try again deal) “the glove box operators guide explains this”
You crank the engine, and the above list of logic checks, must not fail, during the start event or it cuts the ASD.

Note carefully, if spark is bad cranking, the ASD cuts spark coils 100% dead.(double dead) Funny, but very true, see the ASD schematic? The ECU gives but 2 seconds to wake up and work, or kills the show.

You only get 2 seconds to get the 8 factors above true or the game is all over.
If when driving, it (PCM) sees one of the 8 fail, ASD drops.
In fact, the ASD can drop, then come back, while driving, people say it cuts out. sure it did, on 1993 and newer JEEPS you can scan, drive and log data, to see why! any OBD2 scan tool. one that logs is, best of best.
The USA has all cars OBD2 1996 and newer and cheap scan tools can be had for $9, rented or loaned to you. (there is no reason, to work blind, ever in the USA, get the scan tool, plug it in and USE IT) (if older use the blinking CEL checks seen below…)

The DTCs errors, tell you. CMP /CKP or Spark are dead. (and unique codes for ASD failures input or outputted)
OBD2 we check Pending DTC’s and LIVE and Stored DTC’s.
Freeze frame, DTC’s, will show what DTC failed. (and what the other sensors were doing at that moment)
and even seeing RPM drop like a rock, faster than any crankshaft can spin down, dig? is one more clue.

On pre 1996 Jeeps see how to get flash codes below:
The FSM covers that under emissions + diagnostics. See DTC list and how to get it. (hint :crank for 5 seconds, see what fails?)
The FSM is here.

Jeep knowledge base

FLASH codes, or OBD scans: 
DTC scanning methods from first Jeeps to new. How to get my DTC errors; there are 2 ways. I use a real scan tool for all 91 to now.
Here is my Innova 3120 ($129 at walfart too){ does Jeep: 1993-1995 OBD1 and then does OBD2 1996 to Now. but does not do OBD2 Live-Data Stream Display )

The ignition key toggle tricks works 1991? to now., 1996+ Jeeps, a scan tool must be connected to the OBD2 port to diagnose any ASD issues, below is a list of codes that will shut it down. (OBD2)
Key trick is (On/off/On/off/On/ ) see CEL (MIL) flash 2 digit codes now… “no start? crank for 5 seconds., release key and see codes? might work too.?”
Jeep changes codes like gals change lips stick colors.
All decimal codes, FSM uses hex. (base 16)
Warning, the CEL may not glow for many errors running. even code 54 will not glow the CEL. (scan tools rule here)
At the end it will flash two fives, which means end of codes
DTC’s: the 2 digit are OBD1, the Pxxxx codes are OBD2. P means powertrain, engine or transmission codes. (errors)

  • 11 CKP crank sensor dead. 1996/7 (P1391) (P1398) misfire at limit! CKP is an EPA requirement for 1996 rules. (misfire,etc)
  • 24 TPS stuck high, cuts fuel. (P0123) “throttle position sensor’
  • 42 ASD fails up to 1998 or can mean the Fuel pump relay output is DEAD. See FSM for details.
  • 43 Dead spark (primary side) DTC errors (P0351)
  • 54 (1993 my oldest book) means “no cam shaft sync signals”, CMP. (1996/7) CMP = Cam position sensor. (or CMP is misfiring)
  • (9D-hex? factory DRB? scan tool) ( or OBD DTC P1391) CMP/CKP loss. (1998+ code)
  • I’m sure there are other codes, that can drop ASD, but jeep does NOT list them all. Thus my page.
  • 37 Park / neutral switch PRNDL failure? (I’m guessing here) and beyond here. code 14/24/? The jeep books do a poor job of stating all ASD logic. IMO!

The ASD power feeds can blow the PCM fuses, here is the long play (45min) part 1 to 3, video for students on that topic, finding the PCM dead…

Finding out ASD states, for DIY, with almost no tools, (no scan tools? ) NO STARTS?
The ASD relay most not drop out cranking for 5 seconds?
Gee, how can I discover that? well, lots of way.
Keep in mind, most folks can’t hear the pump spin cranking (or drop out cranking! ), (unless Xmen folks? “or Superman?)

  1. The scan tool told you why! (DTC) but you don’t have one.. for $123? bucks even less used!!!. so… here is a cheaters list…
  2. The ASD relay coil pins went from 12vdc (11v) to 0v, 2 seconds, before my 5 second cranking session ended. This is the ECU doing that for “CAUSE”.
  3. My spark timing light connected, went dead, at 2 seconds, same as per above. per “CAUSE”.
  4. My voltmeter at 2 fuel pump wires went from 11v to 0v in 2 seconds. per “CAUSE”.
  5. My injector (any) NOID light (connected) goes dead, 2 seconds in to cranking, for “CAUSE”.
  6. IF not, then the fuel pump is most likely dead. Check fuel pressure next. to be at spec, not dribble tests malarkey. Injectors need full spec. pressure to run. Sorry, dry rails is a valid test, but not the dribble test.
  7. What is “CAUSE”. Well that is easy, I just listed all ECU ASD drop Causes above, all 8. Having no scan tool, makes you blind, get one and stop working BLIND! (beg, barrow, rent or buy one )

The keyon/off magic tricks sadly, clears many ASD drop failures. Making that trick near useless. (key off, erases some DTCs)

Dog chases trail?:
Please do not take your car to the dealer and say, my CEL was on, before, but is not on, now. oops!
The PCM only reports live codes (old codes are cleared automatically, if no longer true) (Live means NOW)
In the real world, things can be good, bad or intermittent. (buy a scan tool and log your failures in real time live, and then you have facts that can solve complex problems, and guess what?, newer cars are more complex and there is no end to this,evolution…)
The ECU stores codes, but if they self corrected, they are ERASED, (sorry the dealer can NOT see erased codes by the PCM or by your resetting them, with the scan tool or battery pulls) (there is no Windows undelete command, in cars, not yet…)
If you ask them to fix cleared codes, at the dealer you will spend lots of cash and get zero results. (it’s an Implied, demand by you; for him to GUESS, so you are asking him to guess, he is not god. nor clairvoyant, he is but only a man)
In most cases, EVERYONE, and me, all guess wrong about equal, lacking FACTS or EVIDENCE.
So, buy a $9 scan tool and get the DTCs your self,write them down and the mechanic can guess 10 times better now. even 100 times is possible (eg, intermittent open OXYGEN sensor heater. for sure)
One more odd thing, is the ECU/PCM on most cars loves to hide bad spark DTCs, you key off and it erases the bad spark DTC. (this is to give it a new chance, next crank up, IMO)

More… (one more case of the chicken and egg) see why?

The older Jeeps, say a 1995, has OBD1, and most folks, don’t have a Scan tool.
The key on/off/on/off/on trick erases spark failure codes. (sucks huh?)
On 1991 and newer Jeeps, the scan tool can, see bad spark DTCs. (try it)! Cranking for 5 seconds. Look for Spark fail or other codes. (DTCs)

Scan tools for old dogs:
This tool can do real scans on 1993/1995 Jeeps.
Older than that, only $1000 and up scan tools work,
DRB2, (DRB is the factory scan tool name,btw)
Snap-On MT-2500.
The older 87-90′ Renix EFI (ECU) will not even store codes, it only does live errors.

Buy an old DRB2, off fleabay. 91 up 95? $$$$$
AutoXray 5000, or 6000 used
OTC monitor 4000, used.
Actron CP 9110

RENIX history: (super old Dogs) I owned 2.
Model years: (find a working scan tool for these engines, is problematic. )
The Renix EFI is AMC system. its not a JEEP it’s AMC. and is NOT OBD1 at all. (it’s pre OBD1 or as they say Proprietary.)

  • 1986 – Renix TBI available on Jeep 2.5 L four-cylinder engines.
  • 1987 – the new Renix controlled 4.0 L six-cylinder engine was rated at 173 hp (129 kW; 175 PS) and 220 lb·ft (298 N·m) of torque.
  • 1988 – 4.0 L output increased to 177 hp (132 kW; 179 PS) and 224 lb·ft (304 N·m) of torque, due to higher compression ratio.
  • 1989 – Changed to Renix MPFI.
  • 1991 – Chrysler Corporation (then the owners of the Jeep brand replaced the Renix control system with OBD-I-compliant control electronics, the Chrysler HO EFI).

Jeep History helps.
The marque has gone through many owners, starting in 1941 with Willys, which produced the first Civilian Jeep (CJ).
Willys was sold to Kaiser in 1953, which became Kaiser-Jeep in 1963.
American Motors (AMC) bought the company in 1970.
The Chrysler Corporation bought out AMC in 1987, shortly after the Jeep CJ was replaced with the AMC-designed Jeep Wrangler or YJ.
Finally, Chrysler merged with Daimler-Benz in 1998 to form DaimlerChrysler.
and now is Fiat in 2009.
They did continue to use “AMC” parts until the stock was depleted.

by :

Just fast journal here, for friends with bad ASD…

My 2008 JK jeep ignition coil. (the PCM monitors this coil, for bad primary signals)
2008 JK jeep ignition coil
My JK Jeep the PCM might throw P2302 ionization error, and the FSM don’t even mention bad spark plugs or the HV wires. (which causes this?, a 102,000 mile service point, that folks SKIP, bad spark plugs/wires)
Both Spark plugs must fire, and conduct or the primary current will NOT be correct and the ECU throws, IONIZATION errors.
What this is, is the spark plasma at the spark plug tips. The spark actually Ionizes the Air and fuel charge, what we call FIRING. (the plasma forms a live resistor that the ECU reads, INDIRECTLY)
If there is no spark, there is no plasma and the coil primary current will be too low.
This is what the test does, and is not explained well, in the FSM.
The Wranglers got 3 coil pack system, about 1996 (4.0L) but the 2.5 was still distributor system, the Grand Cherokee ran this distributor until 1998 (and some COPS) where they switched to COP coils in 1999 for each spark plug, Coil Over-Plug.
By 1999 all gas engine were COP. 3.7 to 6.2Liter. (except the 4.0L)
The last 4. liter I-6 Jeep engine was at end of the 2006 model year. (used in Wrangler) over 5 million produced as of 2001,then Surplanted with the 3.8L.
In each case, you have 1 coil, 3 coils (coil rail or pack) or 8 COPS. ( a fast glance at your engine, and bingo, what you have is there)
I mention all this, just for if you have ASD relay issues due to primary ignition spark failure.

Best place for asking questions is FixKick forum.

8 thoughts on “Jeep ASD relay magic or not? Automatic Shut Down relay”

  1. 1994 jeep Cherokee, started bucking, when in normal driving operation 40-60 MPH, it would do this this every few days, sometimes maybe just once and other times 5-6 times, but would buck and run fine ? The last time I ran it it went a half mile, bucked and stalled for the first time ???? Another issue, maybe, if it sits for a few days it is sometimes hard to start, maybe not starting at all, especially after a rain or cold weather. Need help.

  2. my first comment ever here, a new feature here, wow.
    Jeep bucking, well most times (lots of causes) is bad spark,
    THE ASD relay is first thing to WATCH, if it drops out, the scan toll for 1995 (max year) will show why it dropped.
    the ASD can be called the anti burn relay, it drops off line to prevent fueling fires. (by laws too.)
    on other cars all we do (firmware) is cut injectors dead.
    The bucking is not really fuel cut, as that tapers off easy not buck.
    Bucking is lost spark, or ASD drop out.
    There are only 2 ways to diagnose any jeep and #1 is owning a scan tool.
    Let me guess you have no such tool (Innova makes one)
    the second step is monitor in the ASD relay, I use a voltmeter wired to it and then to the passenger seat or floor boards.
    I monitor it its output or the coil 2 pins, to see if it drops off line at the BUCK if it does BINGO, scan it.
    The PCM(ECU) runs the logic on said ASD relay and has many rules for it dropping out all covered in the FSM (factory service manual do you have book? its always the best way)

  3. i did not remember my old posts now 10 years ago.
    my list is out of the book by jeep FSM, clear as day facts.
    ASD drop rules. (jeep does not do this well at all , the documents) but does this.
    DTC errors.
    24 TPS stuck high, cuts fuel. (P0123) “throttle position sensor’ bad TPS or connector fell off or ground wire to it broken off.
    42 ASD fails up to 1998 or can mean the Fuel pump relay output is DEAD. See FSM for details. (not yours)
    43 Dead spark (primary side) DTC errors (P0351) this is the spark coil tachometer signal and if dead ASD drops off line.
    54 (1993 my oldest book) means “no cam shaft sync signals”, CMP. CMP = Cam position sensor. (or CMP is misfiring)

    I’m sure there are other codes, that can drop ASD, but jeep does NOT list them all. Thus my page.
    37 Park / neutral switch PRNDL failure? (I’m guessing here) and beyond here. code 14/24/? The jeep books do a poor job of stating all ASD logic. IMO!

    really best is drive , buck and scan at the same time, use 1995 scan tool, ask.
    the record all DTC errors. found at BUCK time, BINGO you know why, tell your DTCs and we can work from THERE.

  4. 2010 jeep cherokee kk 3.7.

    Was running well one day and then all of a sudden CEL on. Scanned and code came back p0306 (misfire cyl. 6)

    Took it to local jeep dealership, had coilpacks tested all came back fine, new leads and plugs, still no change, lastly cleaned fuel injectors. Checked codes no code came back. Drove out of the dealership 15 mins later CEL back on, same code p0306.

    I am running out of ideas and am sick to death of dealing with the dealership, do you think this asd related and is there anyway to troubleshoot it if it is?


  5. you might have a lot of knowledge but your attitude is that of an arrogant asshole. I got half way thru this read and was thoroughly insulted. no thanks

  6. 2007 Liberty. Good alternator, good , changed PCM. No charge voltage. There is no battery temp sensor that I can find. Could the battery reference wire to the pcm be bad? P0038. P0452. Are the only codes. I’m 250 miles from home, broke, need advice what to look for

  7. 2016 Jeep Wrangler freedom edition…driving on highway going about 70 and everything shut down. All gauges, no power steering…I got the Jeep to the shoulder and turned it back on and it ran. What would cause this?

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