1999 Jeep Wrangler TJ Will Not Start
- Thread starter Westlotorn
- Start date
We started with sending ours in for a rebuild, they sent it back with our check and said it tested perfectly, they did not take our money. Very nice of them to check it and confirm but I am still looking for answers. I think it is in the wire harness.
Since I have ordered another PCM, I was visiting with a friend that had a 2007 I believe; he told me that he had to have his KEY REPROGRAMED! .... now that’s some food for thought. My PCM will be plug n play, meaning that it will be flashed based on the factory key. Just maybe the ole girl is doing exactly what she’s supposed to be doing... wrong key?
Cam position sensor tells the injectors when to open, it has nothing to do with the fuel pump or pressure in the fuel rail.
Yup. In my case I have 48 PSI at the rail and wet plugs so injectors are working, I assume that means cam sensor is good, I know fuel pressure is on a separate circuit.
Still trying to get this TJ back on the road.
In the OBD2 port I have found the #3 CCD Bus pin is showing 2.48V and I understand it should show 5 Volts. Pin 6 the SCI Receive is showing 4.258 volts and pin 7 the SCI Transmit is showing zero or dead volts. I used the wire schematic and traced these two wires back to the computer, one goes to the Gray plug at the PCM pin # C2727 listed as SCI Transmit and the other SCI Receive goes to Pin C29 in the gray plug. Both wires test good but are not getting the correct output from the computer.
All the grounds and power pins are good in the Black PCM plug.
Most of the Jeep is torn apart now for access and tracing wires.
I have removed, cleaned, wiped with dielectric grease every ground I have discovered, again following the Wire Schematic.
Right now I am thinking the PCM/computer is bad but it was tested and sent back to me with a note saying it tests good.
What still concerns me are the other electrical issues and wondering if these are all connected.
1. No Start, but turns over well
2. When I pull a plug wire and put a spark plug in the wire and turn the engine over I get good blue spark on all 4 cylinders.
While turning over spraying starting fluid into the throttle body does not do anything so the spark I see must be happening way out of time. Crank Position Sensor was tested, tested good, replaced still no change. Plugs are wet with fuel when pulled out after no start cranking. With plugs out I point my propane torch at the spark plug holes and they instantly pop burning the fuel in the cylinder so there is fuel and it does burn. So Spark is way out of time, reading says the computer/PCM takes information from the crank sensor and cam sensor and times the spark to the spark plugs. This is not happening. So computer issue or Cam Sensor issue?
3. No Volt gauge, it does not read or move when the key is turned on.
4. No Tach movement when engine is cranking
5. Fuel gauge goes straight to showing 100% full, tank is not actually full.
6. Headlights not working when switch is pulled out but the high beams do work for both flash and when locked on.
Interior lights do work, horn works.
No fuses have blown.
7. In the power distribution center under the hood the small fuses in this block, all in the top row closest to the front of the car are dead, not blown but no power reaching these. In the wire schematic page 8W-10 it lists these as 1-2, 7-8, 13-14, 19-20. Again no fuses are blown but these have no power reaching them.
I tried applying 12V to these with a hot wire hoping to fire things up with no results, nothing changed that I found and again no fuses popped.
The search goes on.
I am still at a loss trying to figure out why so many functions are bad at the same time. Thanks for any consultation offered, this one is playing hard to fix.
Although I see SCI in the schematic with receive and transmit it does not say what the SCI is or how it functions. I have not been able to determine what SCI stands for? Anyone?
In the OBD2 port I have found the #3 CCD Bus pin is showing 2.48V and I understand it should show 5 Volts. Pin 6 the SCI Receive is showing 4.258 volts and pin 7 the SCI Transmit is showing zero or dead volts. I used the wire schematic and traced these two wires back to the computer, one goes to the Gray plug at the PCM pin # C2727 listed as SCI Transmit and the other SCI Receive goes to Pin C29 in the gray plug. Both wires test good but are not getting the correct output from the computer.
All the grounds and power pins are good in the Black PCM plug.
Most of the Jeep is torn apart now for access and tracing wires.
I have removed, cleaned, wiped with dielectric grease every ground I have discovered, again following the Wire Schematic.
Right now I am thinking the PCM/computer is bad but it was tested and sent back to me with a note saying it tests good.
What still concerns me are the other electrical issues and wondering if these are all connected.
1. No Start, but turns over well
2. When I pull a plug wire and put a spark plug in the wire and turn the engine over I get good blue spark on all 4 cylinders.
While turning over spraying starting fluid into the throttle body does not do anything so the spark I see must be happening way out of time. Crank Position Sensor was tested, tested good, replaced still no change. Plugs are wet with fuel when pulled out after no start cranking. With plugs out I point my propane torch at the spark plug holes and they instantly pop burning the fuel in the cylinder so there is fuel and it does burn. So Spark is way out of time, reading says the computer/PCM takes information from the crank sensor and cam sensor and times the spark to the spark plugs. This is not happening. So computer issue or Cam Sensor issue?
3. No Volt gauge, it does not read or move when the key is turned on.
4. No Tach movement when engine is cranking
5. Fuel gauge goes straight to showing 100% full, tank is not actually full.
6. Headlights not working when switch is pulled out but the high beams do work for both flash and when locked on.
Interior lights do work, horn works.
No fuses have blown.
7. In the power distribution center under the hood the small fuses in this block, all in the top row closest to the front of the car are dead, not blown but no power reaching these. In the wire schematic page 8W-10 it lists these as 1-2, 7-8, 13-14, 19-20. Again no fuses are blown but these have no power reaching them.
I tried applying 12V to these with a hot wire hoping to fire things up with no results, nothing changed that I found and again no fuses popped.
The search goes on.
I am still at a loss trying to figure out why so many functions are bad at the same time. Thanks for any consultation offered, this one is playing hard to fix.
Although I see SCI in the schematic with receive and transmit it does not say what the SCI is or how it functions. I have not been able to determine what SCI stands for? Anyone?
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The distributor is rotating and the rotor inside the cap points directly at #1 when the crankshaft is turned to face the TDC mark on the harmonic balancer. If the cam was not turning properly these two would not still be in alignment. Thanks for the thought, i wish it was mechanical, I could pull the timing cover and replace the timing chain in 3 hours and be done, that would be a blessing in comparison to this electrical issue.
Have you tried to read the OBD codes with the ignition key On - Off - On - Off - On within 5 seconds method?
There are 4 main engine grounds (page 8W - 90 - 17 in the 1999 FSM). Check all of them and make sure that they're all good. I'd also check both battery cables.
There are 4 main engine grounds (page 8W - 90 - 17 in the 1999 FSM). Check all of them and make sure that they're all good. I'd also check both battery cables.
Replaced the PCM and fired right up. All the gauges are working properly and OFB II is communicating as it should. Next week is radiator leak. Thanks for the help.
Glad you won the battle, I am still in the trenches. Congratulations.
I unplugged my PCM completely and the fuse with the dead ground is still grounded, that fuse feeds the O2 Sensor and the Leak Detection System. I unplugged both of those devices and still have the dead ground. Wiggle all wires I can touch, still dead ground. I am pulling the under hood fuse box apart to inspect all wires and feeds.
I unplugged my PCM completely and the fuse with the dead ground is still grounded, that fuse feeds the O2 Sensor and the Leak Detection System. I unplugged both of those devices and still have the dead ground. Wiggle all wires I can touch, still dead ground. I am pulling the under hood fuse box apart to inspect all wires and feeds.
Jeepn_Texas
TJ Enthusiast
Update: Jeep will not start, still.
Assuming the computer/PCM is good because we sent it off for rebuild and it was sent back to us with a note saying it was good and we were not charged. This was the start of this no start issue.
After tearing into the entire Jeep, tracing and testing nearly every wire for continutity and tracing power sources end to end I have decided the PCM must be the problem. Things learned along the way.
Everyone agrees the grounds must be perfect for all to work. I traced and checked all grounds I could find. The FSM (Factory Service Manual) available in the sticky thread on this forum is a huge help but it is almost 1,500 pages so plan on spending some time learning and studying when you venture down this road.
The SCI Port stands for Serial Communication Interface, the SCI wires send signals on the + and - wires to the PCM and to the data port/ OBD2 port under the dash. The FSM always calls the OBD2 port a Data Port. My OBD2 port is dead, will not connect to a code reader.
The SCI Data wires do not respond, they are fed by the PCM but testing of these wires say they are good from the port to the PCM.
The PCM is not sending information.
The O2 sensors have 2 white wires that are the heater for the O2 sensor on cold start. These white wires attach to the 5V feed from the PCM for power. These will show a ground when connected to the 5V feed if the 5V feed does not have power.
THIS threw me for quite a while trying to see why the circuit was grounded looking for dead wires. The problem in testing was I tested one at a time. The second O2 sensor heaters were on the same wires so I kept getting the same results until I dis connected both at the same time and the light came on. I had been chasing a non issue. Learning curve, time wasted.
The ASD ( auto shut down relay) is a simple relay but if it does not engage your engine will not run. The ASD is connected to 4 wires.
B1. Red White, main feed with key on 12V from 30A fuse in the PDC fuse #6. PDC is Power Distribution Center, should be named UnderHood fuse block. 30A is one of the large fuses
B2. #14 size wire Dark Green with pink stripe this wire is dead unless the ASD is active. It is 12V when engaged
B3. smaller 12 V feed from Fuse 12 in the glove box fuse box, gets power from the key switch, this is hot all the time if key is on and only powers the magnetic trip inside the Relay.
B4. is a dead pin, no wire attached
B5. #18 size wire Dark Blue Yellow stripe from the PCM/computer. This wire is a ground signal from the PCM. This is the Off/On wire for this Relay, if you wish to test the relay, turn your key on and touch this blue wire with a ground test lead. The relay will click on.
For B5 to turn on via computer signal the computer must see a good information feed from the Crankshaft Sensor, Camshaft Sensor and I believe the Fuel Pump is tied in somehow.
Note: as you turn on the key there is a 1.8 second time period where the ASD will activate, if it does not get the proper signal back from the Crankshaft and Camshaft sensor, Coil, A4 sensor ground, the ASD will turn off.
Another twist for you, if your ASD does not power up their are three fuses that don't power up also because they get power from the B2 pin on the ASD Relay, the Dark Green Wire with Pink Stripe, DK/PK
The #27 fuse and the #21 and #18 fuses in the underhood PDC Power Distribution Center will be dead. These are the fuses closest to the 4 relays. This also threw me, I checked my fuses right away to see if they were not blown and all were good, you need to also check to see if they are powered up with the key on. If not the ASD relay is not engaged.
Cheat Sheet for reading the wire diagrams and trying to make sense of them.
PCM this is your computer Power Control Module
PDC Power distribution center Under Hood Fuse block
Data Link Connector This is the OBD2 port under your dash where you plug in the scan tools
Fuse Block this is the fuse block behind your glove box in a TJ.
Other tips
all wires are noted in the schematics by size of wire IE: 14, 16, 18, 20 gauge.
It is noted if they are fused "F" or non fused "A" IE: F20
The color of each wire is also indicated IE: OR/G = orange with green stripe. The FSM has a page that shows each color if needed.
K - before the wire tells you it is a PCM interface wire
Z- before the wire tells you it is a PCM interface ground wire
V - wire goes to switches or solenoids
L - Lighting wire exterior
M- lighting wire interior
F- any fused wire, protected by a fuse
A - any wire unprotected by a fuse + battery wire
G - ground wire
E - dimming light circuit
D- data link wire OBD2 port wires
C- IE: C103 shows any connector, where wires can be disconnected
8W-90-1 shows all connectors and locations
S - Splice where wires are joined but continue as one after the splice
There is a Section in the FSM that shows all splices 8W-95-1
The PCM has 3 main connetors Don't disconnect or connect these with Key On you can damage the PCM.
C1 Black connector at the PCM
C2 White connector at the PCM
C3 Gray connector at the PCM
In my case the crank and cam sensors appear to be working fine but the signal to the computer is not turning the ASD on. Even when I engage the ASD by grounding the B5 ASD pin which supplies power to my dead circuits this jeep will not start.
After testing the wires to be sure they are good I have come to the conclusion my PCM/computer is dead.
I wrote this to help save the next poor soul from having to look up all this stuff. It takes forever to learn all the acronyms so I could start tracing the wires properly.
I knew nothing about a Jeep Wire system when this started. Now I know a lot I wish I did not have to learn. Hope it helps the next guy get fixed faster. I will follow up when I get a new PCM and test it.
I have concluded my headlight issue may be separate but the gauges not working is typical of the PCM failure.
My nephew had been driving this jeep before it failed and maybe he did not notice the headlight issue.
Assuming the computer/PCM is good because we sent it off for rebuild and it was sent back to us with a note saying it was good and we were not charged. This was the start of this no start issue.
After tearing into the entire Jeep, tracing and testing nearly every wire for continutity and tracing power sources end to end I have decided the PCM must be the problem. Things learned along the way.
Everyone agrees the grounds must be perfect for all to work. I traced and checked all grounds I could find. The FSM (Factory Service Manual) available in the sticky thread on this forum is a huge help but it is almost 1,500 pages so plan on spending some time learning and studying when you venture down this road.
The SCI Port stands for Serial Communication Interface, the SCI wires send signals on the + and - wires to the PCM and to the data port/ OBD2 port under the dash. The FSM always calls the OBD2 port a Data Port. My OBD2 port is dead, will not connect to a code reader.
The SCI Data wires do not respond, they are fed by the PCM but testing of these wires say they are good from the port to the PCM.
The PCM is not sending information.
The O2 sensors have 2 white wires that are the heater for the O2 sensor on cold start. These white wires attach to the 5V feed from the PCM for power. These will show a ground when connected to the 5V feed if the 5V feed does not have power.
THIS threw me for quite a while trying to see why the circuit was grounded looking for dead wires. The problem in testing was I tested one at a time. The second O2 sensor heaters were on the same wires so I kept getting the same results until I dis connected both at the same time and the light came on. I had been chasing a non issue. Learning curve, time wasted.
The ASD ( auto shut down relay) is a simple relay but if it does not engage your engine will not run. The ASD is connected to 4 wires.
B1. Red White, main feed with key on 12V from 30A fuse in the PDC fuse #6. PDC is Power Distribution Center, should be named UnderHood fuse block. 30A is one of the large fuses
B2. #14 size wire Dark Green with pink stripe this wire is dead unless the ASD is active. It is 12V when engaged
B3. smaller 12 V feed from Fuse 12 in the glove box fuse box, gets power from the key switch, this is hot all the time if key is on and only powers the magnetic trip inside the Relay.
B4. is a dead pin, no wire attached
B5. #18 size wire Dark Blue Yellow stripe from the PCM/computer. This wire is a ground signal from the PCM. This is the Off/On wire for this Relay, if you wish to test the relay, turn your key on and touch this blue wire with a ground test lead. The relay will click on.
For B5 to turn on via computer signal the computer must see a good information feed from the Crankshaft Sensor, Camshaft Sensor and I believe the Fuel Pump is tied in somehow.
Note: as you turn on the key there is a 1.8 second time period where the ASD will activate, if it does not get the proper signal back from the Crankshaft and Camshaft sensor, Coil, A4 sensor ground, the ASD will turn off.
Another twist for you, if your ASD does not power up their are three fuses that don't power up also because they get power from the B2 pin on the ASD Relay, the Dark Green Wire with Pink Stripe, DK/PK
The #27 fuse and the #21 and #18 fuses in the underhood PDC Power Distribution Center will be dead. These are the fuses closest to the 4 relays. This also threw me, I checked my fuses right away to see if they were not blown and all were good, you need to also check to see if they are powered up with the key on. If not the ASD relay is not engaged.
Cheat Sheet for reading the wire diagrams and trying to make sense of them.
PCM this is your computer Power Control Module
PDC Power distribution center Under Hood Fuse block
Data Link Connector This is the OBD2 port under your dash where you plug in the scan tools
Fuse Block this is the fuse block behind your glove box in a TJ.
Other tips
all wires are noted in the schematics by size of wire IE: 14, 16, 18, 20 gauge.
It is noted if they are fused "F" or non fused "A" IE: F20
The color of each wire is also indicated IE: OR/G = orange with green stripe. The FSM has a page that shows each color if needed.
K - before the wire tells you it is a PCM interface wire
Z- before the wire tells you it is a PCM interface ground wire
V - wire goes to switches or solenoids
L - Lighting wire exterior
M- lighting wire interior
F- any fused wire, protected by a fuse
A - any wire unprotected by a fuse + battery wire
G - ground wire
E - dimming light circuit
D- data link wire OBD2 port wires
C- IE: C103 shows any connector, where wires can be disconnected
8W-90-1 shows all connectors and locations
S - Splice where wires are joined but continue as one after the splice
There is a Section in the FSM that shows all splices 8W-95-1
The PCM has 3 main connetors Don't disconnect or connect these with Key On you can damage the PCM.
C1 Black connector at the PCM
C2 White connector at the PCM
C3 Gray connector at the PCM
In my case the crank and cam sensors appear to be working fine but the signal to the computer is not turning the ASD on. Even when I engage the ASD by grounding the B5 ASD pin which supplies power to my dead circuits this jeep will not start.
After testing the wires to be sure they are good I have come to the conclusion my PCM/computer is dead.
I wrote this to help save the next poor soul from having to look up all this stuff. It takes forever to learn all the acronyms so I could start tracing the wires properly.
I knew nothing about a Jeep Wire system when this started. Now I know a lot I wish I did not have to learn. Hope it helps the next guy get fixed faster. I will follow up when I get a new PCM and test it.
I have concluded my headlight issue may be separate but the gauges not working is typical of the PCM failure.
My nephew had been driving this jeep before it failed and maybe he did not notice the headlight issue.
Thanks Westlotorn.. I have one just like yours and I am saving this info in case I may need it. Sure hope it's the PCM.
Good Luck for a change !!!!!
Good Luck for a change !!!!!
Looked at the Headlight issue today. Wires tested fine for both regular and high beams, grounds tested fine. Both Low Beams were just burnt out. My nephew had been driving this and never mentioned this small detail. I am thinking he was using the high beams just to keep it on the road. He was working really long hours so I will give him a little slack but he still may get the earned head slap for not fixing a burned out headlight and then having two burned out headlights. Both were Sylvania, might need a new brand but glad to find one easy fix.
Well, the new computer that was said to be IN STOCK when ordered now 2 weeks ago has not yet arrived. As of Thursday it had not shipped yet. Add clearly says in stock and will ship right away. I guess that is subjective information. I will update when this arrives.
This was from FS1. I did contact Wranglerfix prior to ordering from FS1 but they did not get back to me other than a note that said they would get back to me?
Maybe my 1999 2.5L 5 speed manual Calif edition PCM is very unique and hard to get.
EDIT: FS1 responded as I typed that the PCM will ship in 2 days and they apologized for the delay. So I will be over 3 weeks on delivery time. FYI.
This was from FS1. I did contact Wranglerfix prior to ordering from FS1 but they did not get back to me other than a note that said they would get back to me?
Maybe my 1999 2.5L 5 speed manual Calif edition PCM is very unique and hard to get.
EDIT: FS1 responded as I typed that the PCM will ship in 2 days and they apologized for the delay. So I will be over 3 weeks on delivery time. FYI.
Second update. FS1 responded once again, this time they say it will ship within 48 hours, and they gave us a tracking number. My experience is that tracking numbers are assigned at time of pick up not 24-48 hours in advance of shipping. Oh well, still hoping it fires up with the new PCM installed.
Next time go with @Wranglerfix. FS1 is a joke.
I'm hoping it works out for you though. Let us know how it goes!