Recently I had problems with the car that was finally resolved by replacing the MAF sensor. I used another site to find a solution and was simply told to replace one component after another. I was told to replace the ICU, the cam sensor, and the crank sensor until I finally inspected the MAF and found the heated wire was gone. To recap, I have replaced the coolant sensor, the Ignition module, the cam sensor and the crank sensor. After replacing the MAF the car ran great. No problems until two days ago when I started the car in the morning to allow it to warm up and warm up the interior since it is now cold here; about fifteen minutes idling. When I went to leave the car was running a bit rough and when I got inside noticed the check engine light was on. I turned the engine off and then restarted it. The check engine light was off then came back on. I decided to not drive the car. I check the trouble code by shorting the ADL connector and it flashed code 18. A search of the net said that was a cam/crank error. I checked the connectors and they were tight and I could see no breaks in the wiring where they enter the connector. I removed the cam sensor and checked that the magnet was in place and it is.
So, what causes code 18 and what should I do to correct it? Could the new cam sensor or crank sensor be the source? After completing the repairs I have driven the car about four weeks or so without any problems. I have even allowed the car to idle for fifteen minutes or so twice since the weather turned cold without any check engine lights coming on.
Check the sensor's resistances and wiring back to the computer
November, 5, 2011 AT 7:47 PM
Where can I find the wiring diagram for this; so I can traced the wires? There are a lot of wires coming in and out of the computer. Where can I get the info on checking the sensors?
Thanks for your answer.
November, 5, 2011 AT 9:47 PM
No repair manual -you can download online with Mit1 or Alldata for a cheap price
November, 7, 2011 AT 9:48 PM
I am purchasing the GM mechanical and electrical service manuals for my car. While I am waiting for them to arrive in the post I have this question. From reading on the net, a code 18 for this car is a mismatch between the cam and the crank sensor signals. This car has over 300,000 miles on the engine that I know of (third owner of the car). I am wondering if the timing could have slipped; if the timing chain could have slip since the chain is worn for sure and the tensioner could be weak. The car was running great until that morning I allowed it to warm.
November, 7, 2011 AT 10:24 PM
Could be the timing chain has slipped and throwing it out of sequence
November, 8, 2011 AT 1:44 AM
How can I check this for timing chain slipped? I have a scan tool on loan that can also capture the data stream. Would that tell me anything. I have checked the cam wiring and that appears to be OK, the ground terminal was making ground. Checking the crank wires will be harder and will do that tomorrow. I know the timing chain and gear needs to be replace in this engine but was hoping to wait until Spring to do that job.
November, 19, 2011 AT 8:35 PM
I checked all the wiring and they check OK. I also did some voltage tests for the cam and fuel sensor at the PCM connector. Both were at 5 volts as per specs. I rotated the crank and the cam voltage would go from 5 volts to 0 volts, so the cam sensor is working. Could not check the crank sensor output but the car will crank. Could be there is a broken or bent vane on the 18X, but I don't see how that could happen sitting in the driveway warming up. I put everything back together and the car cranked but ran rough. Smoothed out some after it warmed a bit (could be the PCM recalibrating). Engine runs rough. No codes reported or stored but the engine is not idling correctly. Checked the coil packs and the secondary ohms reading on all coils was around 10K ohms (cheap meter); all gave the same reading. I connected a cornwell scan tool and captured the datastream. I can provide information from that if you can tell me what data you need to help me. I did see that the engine is running lean according to the scan tool. This is my only car so it needs to be running again. It ran great after the repairs mentioned above and just happened one morning while warming up.
November, 19, 2011 AT 8:39 PM
Clean out the idle air control and EGR valve also check the actual fuel pressure
November, 19, 2011 AT 10:20 PM
The EGR valve is clean, I did that when I had the previous trouble. Fuel pressure was checked during the previous problem and was within specs. The fuel filter has not been replaced in several years, so I could do that. Easy enough to do a new fuel pressure check. Will check the IAC.
November, 19, 2011 AT 11:01 PM
When you do fuel pressure checks-you do it with and without the fuel filter same goes to the fuel pressure regulator w and w/o the regulator to be accurate atleast this is my way on troubleshooting the fuel system