Mr Anonymous
Tire Wall
What follows is my account of how I diagnosed and eventually solved an intermittent stalling/surging/bucking problem accompanied by a 212 DTC. I apologize for the length 
, but I think it could be helpful to others trying to diagnose similar problems.
I'd been having an intermittent stalling problem for a few weeks recently that I was having a **** of a time isolating. In the middle of all this the CPS died from the water pump ******* on it. In addition to the 211 DTC for the CPS, I was also getting occasional 212 codes. For those who don’t have all the DTC’s memorized, the 212 code is defined by the PC/ED as: Loss of Ignition Diagnostic Monitor (IDM) input to PCM/SPOUT circuit grounded. (FWIW, other sources define this DTC as: Ignition TACH signal was erratic (module/wiring) or SPOUT circuit fault.)
Since I knew the water pump was leaking and affecting the CPS, I performed a front-end 60K and replaced the CPS, timing belt, and water pump. The CID sensor and the accessory belt were replaced about 2 months ago so I didn't replace them a second time. I was hoping the new CPS would solve the problem...
Despite the front-end 60K and good plugs & wires, the stalling actually seemed to get worse. It also was occasionally bucking and surging at steady throttle, sometimes accompanied by a drop of the tach to zero. Often, a couple of gooses to the throttle would bring it back. Other times it would die. Usually it would start right back up again, although sometimes it would immediately stall again, and a few times it wouldn't start for 5-10 minutes.
Since I was confident the CPS was good and installed properly, and I knew I was getting spark, I suspected perhaps the CID had a problem. I tried a new sensor, but the problem remained. So, I moved on to the DIS. Although the ground to the DIS was good and the DIS tested OK, I tried both adding a separate ground lead to the DIS as well as swapping the DIS with a known good one. The problem was still there. As is often the case with diagnosing intermittent problems, I usually couldn’t get the problem to repeat itself long or often enough to successfully diagnose the problem.
So, after running the KOER several times and passing with flying colors, I started down the checklists from the PC/ED manual.
Everything was checking out OK (at least those things which could be checked with a DMM -- some steps required Rotunda specialty boxes which I don't have). This was becoming increasingly frustrating! I once again verified no vacuum leaks and that all the electrical and sensor connections were clean and intact. Nothing helped.
So, since I had bought one about a month ago but hadn't yet had the opportunity to install it, I replaced the fuel filter. Still no change. I then began to suspect perhaps the fuel pump might be the culprit. Having verified the operation of the ignition system to the best of my ability, and the fact that the symptoms seemed consistent with a fuel flow issue, this seemed like the next logical step. Although the fuel pump hums prior to starting as it should, it seemed to be a little too loud.
I was in the process of waiting to pick up a fuel pressure gauge from a fellow forum member when I looked back at the PC/ED with a fresh eye the next morning to see if there was anything I was missing.
Well, one of the last (or seemingly 'last resort') tests listed for many problems is the 'wiggle' test (as in wiggle the wires to see what happens). I had tried the wiggle test somewhat informally earlier, but couldn't get the problem to repeat itself at that time.
This particular morning, the car wouldn’t stay running for more than a minute or so at a time. I thought to try pulling the MAF connector to see if running the car in open-loop mode might improve the fuel flow sufficiently to keep the car from stalling. When I pulled off the MAF connecter, the car stalled.
Hmmmmm, I thought. So, I started the car back up again and started wiggling the MAF wires. Depending on which way I moved the wires, I could stall the car or keep it running. I felt like I was getting closer...
So, I started examining the connector and the wires. They looked OK, so I then opted to remove the loom, tape and shrink tubing. Everything looked fine. I then realized that although the TPS and coil pack leads originated from different locations on the same harness as the MAF and ACT leads, they crossed over each other beneath the upper radiator hose. I started the car again and managed to stall the car while wiggling the TPS and coil pack wires. So, I pulled of the connectors to both to check them, and VOILA! The R/LG lead (ckt #16) off of the coil pack connector was slit at the bottom of the wire, about 40% of the circumference, about 1 cm from the connector's insulation plug (so it wasn't visible from above), and the wire strands were broken so as to make contact intermittent. The result was irregular firing of the coils due to an interruption in power to the coil pack ultimately causing the intermittent misses and stalls.
A little solder and shrink tubing, and the problem was fixed! I've since put on about 500 miles without a single problem, and she's back to purring like a kitten. thumbs_u
Now, from my examination of the break in the wire, I suspect that the wire itself was split during/prior to the manufacture of the harness/car. Over 8+ years and 84K+ miles, the strands slowly broke, one-by-one, until eventually they all broke and began causing the problems. I also suspect that I exacerbated the problem while squeezing the upper radiator hose to bleed the cooling system both when I replaced the radiator back in April, and more recently after my front-end 60K.
Out of curiosity, I reviewed this circuit in the EVTM to find that this circuit (hot in run or start) is common to the coil pack, CID, CPS, DIS, and PCM, and provides power from the PCM to the ignition components. Obviously, this one circuit has great implications to the proper operation of the entire ignition system! Since the coil pack was operating properly when the circuit was closed, no coil pack DTC's were generated, and there isn't a DTC to indicate a power failure to the coil pack. The 212 DTC now seems logical since the coil pack not firing would cause the DIS to generate a DTC when it lost SPOUT feedback.
So, the moral of this story is that when you've replaced all the key sensors and other components yet still have problems, the 'wiggle' test can be a valuable friend! It also goes to show that with a little persistence and the shop manuals, almost any problem can be solved.
One thing I noticed earlier this summer when replacing the battery/alternator harness is that the harnesses in general, and especially the ones close to or on the motor, have become quite brittle over the life of the car. For the most part the brittleness seems limited to the loom and shrink tubing, but it wouldn't seem a stretch that a jagged piece of loom could damage wires. As another forum member recently traced a transient problem to the main harness as well, I think it’s going to be prudent for folks to begin inspecting their harnesses during routine maintenance and while diagnosing elusive problems.
I also wonder if the defect in the wire was unique to my SHO, or if there was a wider manufacturing defect with this harness. Seeing that a number of people have experienced similar 212 DTC's and stalling even with good CPS, CID, DIS, etc., this might be another route to investigate.
, but I think it could be helpful to others trying to diagnose similar problems.I'd been having an intermittent stalling problem for a few weeks recently that I was having a **** of a time isolating. In the middle of all this the CPS died from the water pump ******* on it. In addition to the 211 DTC for the CPS, I was also getting occasional 212 codes. For those who don’t have all the DTC’s memorized, the 212 code is defined by the PC/ED as: Loss of Ignition Diagnostic Monitor (IDM) input to PCM/SPOUT circuit grounded. (FWIW, other sources define this DTC as: Ignition TACH signal was erratic (module/wiring) or SPOUT circuit fault.)
Since I knew the water pump was leaking and affecting the CPS, I performed a front-end 60K and replaced the CPS, timing belt, and water pump. The CID sensor and the accessory belt were replaced about 2 months ago so I didn't replace them a second time. I was hoping the new CPS would solve the problem...
Despite the front-end 60K and good plugs & wires, the stalling actually seemed to get worse. It also was occasionally bucking and surging at steady throttle, sometimes accompanied by a drop of the tach to zero. Often, a couple of gooses to the throttle would bring it back. Other times it would die. Usually it would start right back up again, although sometimes it would immediately stall again, and a few times it wouldn't start for 5-10 minutes.
Since I was confident the CPS was good and installed properly, and I knew I was getting spark, I suspected perhaps the CID had a problem. I tried a new sensor, but the problem remained. So, I moved on to the DIS. Although the ground to the DIS was good and the DIS tested OK, I tried both adding a separate ground lead to the DIS as well as swapping the DIS with a known good one. The problem was still there. As is often the case with diagnosing intermittent problems, I usually couldn’t get the problem to repeat itself long or often enough to successfully diagnose the problem.
So, after running the KOER several times and passing with flying colors, I started down the checklists from the PC/ED manual.
Everything was checking out OK (at least those things which could be checked with a DMM -- some steps required Rotunda specialty boxes which I don't have). This was becoming increasingly frustrating! I once again verified no vacuum leaks and that all the electrical and sensor connections were clean and intact. Nothing helped.
So, since I had bought one about a month ago but hadn't yet had the opportunity to install it, I replaced the fuel filter. Still no change. I then began to suspect perhaps the fuel pump might be the culprit. Having verified the operation of the ignition system to the best of my ability, and the fact that the symptoms seemed consistent with a fuel flow issue, this seemed like the next logical step. Although the fuel pump hums prior to starting as it should, it seemed to be a little too loud.
I was in the process of waiting to pick up a fuel pressure gauge from a fellow forum member when I looked back at the PC/ED with a fresh eye the next morning to see if there was anything I was missing.
Well, one of the last (or seemingly 'last resort') tests listed for many problems is the 'wiggle' test (as in wiggle the wires to see what happens). I had tried the wiggle test somewhat informally earlier, but couldn't get the problem to repeat itself at that time.
This particular morning, the car wouldn’t stay running for more than a minute or so at a time. I thought to try pulling the MAF connector to see if running the car in open-loop mode might improve the fuel flow sufficiently to keep the car from stalling. When I pulled off the MAF connecter, the car stalled.
Hmmmmm, I thought. So, I started the car back up again and started wiggling the MAF wires. Depending on which way I moved the wires, I could stall the car or keep it running. I felt like I was getting closer...
So, I started examining the connector and the wires. They looked OK, so I then opted to remove the loom, tape and shrink tubing. Everything looked fine. I then realized that although the TPS and coil pack leads originated from different locations on the same harness as the MAF and ACT leads, they crossed over each other beneath the upper radiator hose. I started the car again and managed to stall the car while wiggling the TPS and coil pack wires. So, I pulled of the connectors to both to check them, and VOILA! The R/LG lead (ckt #16) off of the coil pack connector was slit at the bottom of the wire, about 40% of the circumference, about 1 cm from the connector's insulation plug (so it wasn't visible from above), and the wire strands were broken so as to make contact intermittent. The result was irregular firing of the coils due to an interruption in power to the coil pack ultimately causing the intermittent misses and stalls.
A little solder and shrink tubing, and the problem was fixed! I've since put on about 500 miles without a single problem, and she's back to purring like a kitten. thumbs_u
Now, from my examination of the break in the wire, I suspect that the wire itself was split during/prior to the manufacture of the harness/car. Over 8+ years and 84K+ miles, the strands slowly broke, one-by-one, until eventually they all broke and began causing the problems. I also suspect that I exacerbated the problem while squeezing the upper radiator hose to bleed the cooling system both when I replaced the radiator back in April, and more recently after my front-end 60K.
Out of curiosity, I reviewed this circuit in the EVTM to find that this circuit (hot in run or start) is common to the coil pack, CID, CPS, DIS, and PCM, and provides power from the PCM to the ignition components. Obviously, this one circuit has great implications to the proper operation of the entire ignition system! Since the coil pack was operating properly when the circuit was closed, no coil pack DTC's were generated, and there isn't a DTC to indicate a power failure to the coil pack. The 212 DTC now seems logical since the coil pack not firing would cause the DIS to generate a DTC when it lost SPOUT feedback.
So, the moral of this story is that when you've replaced all the key sensors and other components yet still have problems, the 'wiggle' test can be a valuable friend! It also goes to show that with a little persistence and the shop manuals, almost any problem can be solved.
One thing I noticed earlier this summer when replacing the battery/alternator harness is that the harnesses in general, and especially the ones close to or on the motor, have become quite brittle over the life of the car. For the most part the brittleness seems limited to the loom and shrink tubing, but it wouldn't seem a stretch that a jagged piece of loom could damage wires. As another forum member recently traced a transient problem to the main harness as well, I think it’s going to be prudent for folks to begin inspecting their harnesses during routine maintenance and while diagnosing elusive problems.
I also wonder if the defect in the wire was unique to my SHO, or if there was a wider manufacturing defect with this harness. Seeing that a number of people have experienced similar 212 DTC's and stalling even with good CPS, CID, DIS, etc., this might be another route to investigate.
