Notes

Outline

1998 Intrepid 2.7Litre A study of a CMP failure, and recent changes in Chrysler PCM strategy. David Sharp 5 Star Chrysler

Introduction A study of the loss of CMP signal 2.7l. The effects of this loss using coil current ramping as a diagnostic tool. The concurrent effects on other sensor inputs. Scan tool usage in determining the correct path to track reported multiple problems with an OBDII Chrysler vehicle.

Agenda Topics, effects of cmp on coil ramp/on time. Effective use of scan tool to detect loss of sensor input and corrective measures. Effects of extended dwell on coil and injector circuits. How OBDII monitors are relevant to troubleshooting an obvious contradiction.

Overview This study will confirm the overall effect of cmp loss on coil current, extended dwell and PCM adaptive strategies to this problem. Waveforms and scan data will be used to focus on the extended dwell and increased current noted during testing. A few tips to monitor somewhat irrelevant outputs to determine direction when confronted by a intermittent cmp/ckp problem.

Vocabulary Glossary of terms CKP - Crankshaft Position Sensor CMP- Camshaft Position Sensor ASD – Auto shutdown relay MTV- Manifold Tuning Valve COP- Coil on Plug

The Complaint. Customer Complaint: Engine misfiring, stalls, dies, hard starting and surging. This was verified when vehicle brought in. Vehicle stalled upon drive into shop.

The Details This is the scan data without the cmp problem. Glitches were active at this time but not apparent in scan data. Vehicle had stalled upon driving it into the bay. Engine would not restart.  Further findings had revealed that the fuse for the coil/inj had blown. Codes for coils 3 and 4 had been set. Codes for CMP, CKP, and ASD were also present and cleared. Engine ran for a period of 45 minutes with the data that you see here. Warranty clock was ticking. J

Scan Details More scan data during the 45 minutes of bliss. As you can see all is normal for now with exception of the fuel level and adaptives on the high side. Engine was started and stopped during testing to try and duplicate initial problem. CMP/CKP were also monitor with labscope during initial testing. All testing done with A/C active to invoke cooling fan activity.If CKP problem is active and signal is lost, even intermittently, engine cooling fan will quit while fault is active.

The Fun Starts CMP Signal Frame

The CMP Problem First green waveform on previous slide indicates a key on engine off condition. I had shut the engine off, and heard the relays clicking like Morse code. This activity  was abruptly terminated by the circuit during testing. Next wave, in purple was engine was restarted and this was a rendition of the cmp while active. Engine believe it or not, still ran reasonable smooth at this point, but idle quality was deteriorating. Below is I/O before problem. History fuel shut off was due to brake stand to attempt to initiate problem by moving engine, and loading engine in case of harness or load concerns.

The Sensors and What Chrysler Says This bulletin of course is very true. This scenario happens quite often. However, we must concern ourselves with the fact that Chrysler software will still report the wrong sensor even when the problem happens while running, and the engine is not in the start to run transition. I repeated a CKP code on a cmp sensor 4 times on this vehicle with no signals being generated while in the koeo mode. This bulletin applies to all the newer 2.7, 3.2 3.5l engines as well. This particular engine reported 4 false ckp codes on a cmp problem. Indicating the fact that the sensors must be monitored for correct diagnostics. The engine also stalled 4 times without setting any codes or secondary indicators due to cmp signal corruption.

CMP Problem Continued. This is the scan tool indication of the cmp loss. Note that only the crank is indicated as supplying a signal. Note at this time, the fuel level sensor update is now correctly responding to fuel sensor input and reflecting the correct value. Spark advance works normally after the loss of cmp, and is reflecting a correct value for idle conditions. This will normally move up and down by a few degrees as idle quality is trimmed. Note the loss of cmp while running did not cause a stall condition. This was due to a loss, which was an open in this case, and not a corrupted signal.

PCM Reacts to CMP Loss! Look at this reaction to loss of sync! Note engine RPM and TPS position. Engine flares, and if I/O is monitored, one would see a fuel shut off condition. Once you hear this flare, even if not monitoring the data, you can rest assured you have lost the CMP input. With software firing, engine will continue to run normally, with the PCM in full control. I have experimented with many newer Chrysler vehicles, and the flare is consistent with the loss of the cmp signal.

CMP Return Engagement CMP makes a recovery here and the idle flare is duly noted in the I/O screen. Rev limiter has been applied. Note sync is back in, and fuel is being applied.

CMP gets interesting We now have total CORRUPTION of CMP signal. Note fuel/Rev limiter values. This happened just seconds after the last screen. Engine rpm was all over the spectrum, engine was misfiring excessively, then engine dies. Finally after 45 minutes we are getting somewhere. J

Codes set during activity This is the list of codes that were generated during the engine stumble and subsequent stall. Note the addition of the ckp code along with the cmp code. The ASD code was set when engine stalled and cmp continued to send a signal without the engine cranking over. Note: the loss of CMP while cranking will set the Cruise light on, as in previous models. This has been my first experience with this phenomenon and I’m quite pleased to note this. The CMP hall short continued its activity long after the stall. The ASD and Fuel Pump relays clicked like a CPR telegraph room for over 10 minutes, until it had cooled sufficiently.

The Code Parameters No Crank Reference Signal At PCM.      Ignition in start or run, and battery voltage between 4-15 volts. Set Condition:  No CKP signal is detected when engine vacuum is present or cam signals are present. Theory of Operation: The ckp is a hall effect type sensor used to detect the crankshaft speed and position. The PCM supplies 8 volts to hall and sensor ground. The CKP sensor return circuit  has a 5 volt pull up from the PCM. The signal is created by slots in the flywheel. When a slot is under the sensor, the signal is high, when the sensor is blocked, voltage is low. No Cam Signal at PCM. Monitored during engine cranking, after 32 crank position signals. Set Condition: No signal from the cam position sensor while ckp signal is present. Theory of Operation: Same as the CKP. No ASD Relay output at PCM.  Monitored with the ign key on and battery voltage greater than 10 volts. Set Condition: An open or short condition is detected by the ASD relay circuit. Theory of operation: The ASD provides 12 source to Inj/Coils/O2 sensors heaters/SRV/MTV/EGR/and generator. The relay is grounded when the key is in the crank or run position, and rpm is detected. If RPM is not detected, PCM will remove ground to relay. MTV code is self explanatory as its supply source is the ASD.

Coil Activity During CMP Crisis

CMP and Coil Note the green trace, left frame, Key on engine off, short triggers asd/fp. Note the Purple trace, this is the trace that caused the extreme (green) coil reaction in the right slide. The Red trace is a single COP coil being monitored while minute glitches were taking place. This is the reaction discovered by Paul Johnson with his infamous Neon 2.0l. The increase in current is especially evident here, and is a good representation of a minute glitch in the cmp signal and its effect on coil ramp and on time. Note the severe increase in current on the green trace. This is what blew the fuse to the injector/coil circuit when I drove the vehicle in the door. Also note that the ground for numerous coils have not been released and are in continuous dwell. Note the difference in on times as displayed by the blue and yellow traces. The blue trace indicates a problem, was evident at that time, but no codes or glitches were noted. The blue trace was the first indication of problems not quite evident at the moment. The ckp/cmp were out of sync at this time, but not enough to stall engine and report out of sync in blue.

CMP/Coil Putting it all together

CMP Corruption Values ASD and Fuel Pump being cycled with Key on engine off. Engine fan continues to run while cmp values are distorted. Cruise light activates when cmp values are corrupted then sync lost. Engine will not start, but will continue to run when if cmp lost while running. Coil dwell operations severely affected. If  8 volt supply voltage is shorted to gnd, engine will stall, and most times will not restart without disconnecting the battery for a PCM reset. Scan tool PCM reset will not work in this case. Adaptive numerator will have to be relearned before diagnostics continue in this case. CMP signal either shorted to gnd or shorted to voltage will not influence CKP signal. Total loss of CMP while running off idle will not cause stall, and engine will continue to run. Tips If CKP values are corrupted, especially when grounded, engine cooling fan will stop running immediately. Test with A/C on for maximum fan activity. CMP CKP codes will often set together as a single code as the PCM many times Cannot determine which signal was lost so will report both in a single code.

Summary Coil on time and ramp will be affected by sync signal. Severe coil ramp is not always indicative of a failed coil. On time is relative to ramp and vise versa. Software firing is a reality for Chrysler. Further study will have to be applied to CKP failures and Chrysler products. I’ll leave you with one obvious question. Why was there no misfire reported when evidently there was a severe multiple cylinder misfire taking place? Why was this not reflected as a P0300.

Where to Get More Information LTS North and South. iATN Networking/www.iatn.net Your peers. Rumours abound that Chrysler will have an internet repair presence in the next two years.