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Crank, No start and P0122

Empty_Pockets

NAXJA Forum User
Location
Jim Thorpe
Having a no crank condition, first the truck just stalled and died in traffic and set a P0122, and P0700 (trans code set from TPS problems). Cranks but no start, had towed and let it sit, moved harness off of rear head stud, and fuel rail, tied up with zip ties, clear codes restarts no issues. Today, starts no issue, go less than a mile down the road to the store, crank no start resets P0122 and P0700 codes. P0122 will not reset when codes are cleared. Replaced TPS with known good from parts truck, replaced clock spring (for possible sense voltage issue), no change, crank no start. Check continuity from PCM to TPS on all three pins, pin 17 (5v) at black pcm connector, pin 23 (sensor input), and pin 4 (sensor ground), all have continuity. Tested for 5v supply (key on engine off, tps disconnected) at pin 3 (5v supply) on TPS connector, 0V, tested voltage on pin 2 (sensor signal) has 4.4v (should be 0v?), pin 1 (ground) 0v.

Im at a loss but the only thing left are the PCM and the chassis ground. Thought? The autoparts schlub immediately said CKP issue but all he let me say was Jeep Cherokee crank no start. Replace PCM? Harness issue?
Please don't flame me for not using search, Ive searched and checked all the common jeep issues I found from google...Going to get my spare PCM from storge, maybe the harness too. A
*edit* also have a nss problem, probably not related but maybe worth mentioning. Most times I have to start it in neutral because it wolnt crank in park.
 
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Bump, bought my fiance a 99 limited, has the same codes with different issues. P0122 and P0700, stumbles hesitates and stalls but can be started in all gears. Does anyone have a wiring diagram or know if they nss and tps have a common ground?
 
Buy a genuine Jeep Service Manual from PacificCoastManuals.com. The Service Manual has complete wire diagrams. Random stalling can be caused by a faulty Crankshaft Position Sensor.

The P0700 is likely caused by a faulty TPS, or by whatever is causing the TPS code. Ignore the P0700 for now, as it will probably clear up when you fix the P0122. Refreshing all the ground wire connections, including the one at the coil, is a good idea.

P0122 Jeep - Throttle Position Sensor/Accelerator Position Pedal Circuit Low Input

Possible causes

- Faulty throttle position sensor
- Throttle position sensor wire harness is open or shorted
- Throttle position sensor circuit poor electrical connection


TPS TEST

You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.
 
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Any update? Having a very similar problem and haven't figured it out yet.
GF's Jeep (2000 with a 98 block/head and 2000 intake/COP/PCM) started dropping idle the other day every time she came to a stop. No codes at that time. When I took a look yesterday, disconnected the CTS to force it into open loop and voila, runs fine, so i can be fairly confident it's just a sensor issue.
Tested all the sensors on the intake and they all check out fine, but then I started throwing a P0122/0123 immediately after turning on the ignition. Verified that the TPS has 5V reference, ground shows no/low resistance, and signal swings smooth from .8V to 4.04V. I can't imagine how the 122/123 are being set.
Looked into the clock spring/TPS problem, but from what I can tell, that should result in 12V showing up on the TPS 5V reference wire, and >5V on the sensor wire.
Clear the codes and start back up, and both codes show up immediately. All other codes (set intentionally) clear properly every time, so I can be confident the PCM really does think the TPS voltage is both too high and too low.
 
Light came back but without the symptoms. Also having intermittent fuel gauge. It has to be something related to the tps/nss that's the only thing i can think since I have tps and nss issues on both trucks throwing the p0122 code.
 
Oh, forgot to chime back in.
I feel like a bit of an idiot because I'm sure this was just me being an idiot when I swapped motors, but my issue was the positive terminal to the under-hood fuse block. I must have forgotten to tighten down the bolt. Everything diagnostically looked good everywhere I checked, but it's one of those things that's hard to check because it requires tiny vibrations to trigger. Ran fine most of the time, all sensors checked out fine, but throwing the TPS code consistently and a few others very rarely. Tightened the nut and it's been good since.

I vote your issue is power/ground related. The grounds on the block at the dipstick are notorious for corrosion. I just cut them back 12" and re-did them on a few Jeeps. The head - firewall strap is important, but when it goes, the problems are usually obvious. Those smaller ones on the block make for some interesting issues.

But, don't forget about positive. It's just as likely the problem as a ground.
 
I just cleaned the ground yesterday and added a ground strap there. No more issues....so far...now to try it on my 98 and see if it fixes my random crank no start.
 
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