P0688 05 t&c
 

So I wasn't having any problems with my 05 T&C Touring, but it failed to start one morning. It would crank but not catch. Thinking it was a fuel pump issue I brought it to a shop, because I never learn my lesson. After having it for several days, they claimed the fuel pump was fine and I was getting a code 0688 and the engine wasn't getting a spark. They took several readings (they would not provide me with a copy of what, specifically) and claimed it was a bad computer, wanted $1200 to fix it. Paid to have it towed home and replaced the computer myself. No change in the issue. I've inspected the wiring under the engine bay fuse box. There was a small amount of green corrosion which I cleaned off with electrical cleaner and a soft brush, but there did not appear to be significantly damaged wires. I also removed the battery to clean the terminals, wires, and ground. I have never dealt with this code before, and as I understand it, it's just an umbrella warning that can indicate a wide variety of different problems. Unfortunately, between the money the shop charged me, the tow, the new computer, and the cost of the parts I have to replace that were broken by said mechanic, I don't have the funds to take it to another shop. I could really use some input as to what I should look at from here on out because I'm stumped. Thanks in advance.

Which motor is in yours?
Check the coil pack crank and cam sensors.

Sorry for the delay. I have a 3.8L engine. I bench tested the coil pack and all the readings are within normal limits, though it's not putting out a spark. I'll check the Camshaft and crank sensors this coming week.

Alright, so I had tested the Coil pack, and crankshaft and camshaft sensors. Didn't find an issue, but they aren't expensive so I replaced them. Still the same issue. I'm stumped as to what I should check next. I should also mention my code reader is not detecting any codes, though that may be because I keep disconnecting the battery and I've read that you need a special procedure to bring one up in these circumstances. Engine still cranking away but no start.
To Recap:
*Changed PCM (bought it refurbished, but from a company with a good reputation)
*Checked the fuses and wires in the engine compartment fuse box.
*Replaced the coil pack, and the spark plug wires are fairly new
*Replaced the camshaft sensor
*Replaced the crankshaft sensor
*Checked battery charge (it's perfect)
*Fuel pump and fuel line pressure checked by mechanic

RESOLVED: There was a grounding problem in the TIPM (ie: engine fuse box). All the wires, fuses, and other electronics were just fine. The Automatic Shutdown Relay was giving an out of range ground reading to the PCM, causing it to not start.