Codes P0888 and P0700

Code p0700 is in the Engine computer. It just means there is a code in the transmission computer that needs to be read. Code p0888 is the code in the transmission computer that is relevant to this story. It refers to less than three volts at the solenoid pack when there should be twelve volts. That does not have to be due to that wire shorted to ground, although it could be. More commonly it is due to an open circuit, and the most common cause of that is corroded connector terminals, especially if this code sets intermittently.

To know if this is an intermittent problem, all you have to do is observe if the transmission is shifting to the proper gears while on a test-drive. If the problem is occurring, the transmission will be stuck in "limp mode", which is second gear. You have to turn the ignition switch off, then restart the engine to get it out of limp mode. If at any time it shifts properly, even for a little while, the defect is not a permanent failure. That strongly suggests you should be looking for an intermittent break in the wire or at the connector terminals.

Once I posted my reply, this became a private conversation between the two of us, although some of the other experts might add some comments. Be aware that due to a house fire I do not have internet access at home. I drive twenty one miles each night to answer questions, so do not panic if I do not reply right away.

If you try to replace a wiring harness, you will find it is a really huge mess that runs all over the front of the vehicle, and new ones are horribly expensive because they are hand-made. The only time we replace an entire harness is when that is mandated by the manufacturer and the vehicle is under warranty. For everything else, we locate the cause of the problem, then fix it. Some people run new wires, but that is also not desirable. You want to know exactly why that wire developed a problem because it could affect other wires in that harness too. For example, if a harness is laying on the sharp edge of a metal bracket, one wire will rub through first and cause a problem. If that cause is not located, how long will it be before the next one rubs through, and will it be for a circuit that leaves you walking along the highway? Harnesses can also rub back on forth on the body as the engine rocks back and forth between accelerating and braking. I have seen one wire shorting intermittently for the back-up lights, and blowing the fuse repeatedly, and when found, there were another half dozen wires already rubbed bare, but not shorting out, yet. That replacement harness cost over $1,500.00, so obviously we fixed the old one.

How is your understanding of electrical theory? If it is not good, start with a visual inspection of the terminals in the connectors. Look for signs of corrosion on the terminals and for white or light green stuff growing between adjacent terminals. Individual wires in the harness should not be checked yet because that turns it into a mess. Instead, I use voltage measurements to see where it is being lost and where I have it, to figure out the area that has a break. If it comes to that, the circuit needs to powered up, and that normally only happens when the engine is running. To avoid the need to do that, there will be a relay that can be bypassed. Doing that is way easier than trying to describe how to do it, but I can do that too if necessary.

The only time we replace a harness is to replace just a section if it got smashed in a crash. To do that, we cut off a good section from a vehicle in a salvage yard, then splice it into the car's harness. Professionals never never ever use crimp-type butt connectors and especially not Scotch-Lok squeeze-together connectors. Those do not seal out moisture, and will cause a big pile of problems in the near future. My only acceptable repair is to splice and solder the wires, then seal them in heat-shrink tubing. There is even heat-shrink tubing available with hot-melt glue inside to really do a good job of sealing where water can get on them. Also, it is a bad idea to wrap a repaired harness, or a splice, with electrical tape. That will unravel into a gooey mess on a hot day.

Have you tried switching the transmission control relay with one of the other ones like it?

Next, remove that relay, then test for voltage on the four terminals. Ignore the center terminal, if there is one. You should find 12 volts on one terminal all the time. If you do not, check fuse # 9, a 20-amp, in the under-hood fuse box, and check for 12 volts on both sides of it.

If that is okay, reinstall the relay, then go to the solenoid pack and back-probe the red wire. That should have 12 volts on it when the relay turns on. That may not happen until the engine is running and you shift into gear. If it does not, stop the engine, remove the relay, then bypass it with a piece of wire or stretched-out paper clip. If you have the 1" cube relay, that's terminals 30 and 87. If you have the skinny relay, it's the two larger terminals, with the arrows in my nifty drawing. Now you should have 12 volts on that red wire. If you do not, there's a break in that circuit.

If you do have 12 volts on the red wire, it would imply the Engine Computer is not turning that relay on for some reason. That is not real likely because that reason would set the fault code and the loss of 12 volts would just be the result. In this case, the computer is detecting the missing 12 volts which means it thinks it turned the relay on, but didn't see the expected result, therefore the code 888.

Dandy. If you bypassed the relay, then found 12 volts at the coil pack on the transmission, that proves the 12 volt supply circuit is good, and the switched side is good. That only leaves the relay is not being turned on by the Engine Computer. We have two wires to check.

You jumped the two terminals in the relay socket that are for the relay's contacts. We're done with those. Now look at the two remaining terminals. If you're using a digital voltmeter, switch it to the "Ohms" scale, 200 ohms, and put the black probe on the body or battery's negative post. With the red probe, measure at each of those two, (or three) remaining terminals. One should read very low resistance; in the order of perhaps five ohms or less. If you don't find that, the ground wire for the relay's coil has a break in it.

If you're using a test light, put its ground clip on the battery's positive post, then probe the remaining terminals. It will light up when you find a good ground circuit, which is what we're looking for.

If you found the good ground circuit, that leaves the 12 volt feed for the relay's coil, and that comes from the Engine Computer. The fastest way to check that circuit is to stick a thin piece of wire into that terminal, then install the relay. Use that wire as the test point. Don't get carried away. If that wire is fat enough, it, along with the relay's terminal, can spread the terminal in the socket and cause future intermittent problems. If you have the relay box apart so you can see the wires, this is the light green wire. You should see 12 volts there either when the ignition switch is in the "run" position, or when the engine is running, or when it's running and you shift into gear. If you never see 12 volts there, there's a break in that light green wire, or the Engine Computer is not sending the 12 volts there.

If that 12 volts is never there, the next step is to use a scanner to command the Engine Computer to turn on that relay. The engine should not have to be running to do that actuator test. That test allows you to take voltage readings while the circuit is pulsed on and off about once per second. You should also hear the relay clicking on and off. If you never hear that or see 12 volts, the computer is the best suspect, but first check that light green wire for a break, and for a spread or corroded terminal in the computer's connector.

Your first sentence says you found 0 ohms on two terminals. You should only have that on one terminal. If you had the relay in the socket, then you would get a reading to ground on the second terminal, but not 0 ohms. Are you sure the meter was on the 200 Ohms range, and not the 200k range? As I recall, the relay's coil should measure around 50 to 70 ohms, so if you were taking the readings with the relay in the socket, you'd get 50 - 70 ohms from terminal 86 to ground. With the relay not in the socket, you should get a very high or infinite reading from 86 to ground.

A better test is to check for 12 volts on terminal 86. That is what appears to be missing, and that comes from the computer. If you really do have 0 ohms from that terminal to ground, that wire is grounded someplace.

To wrap the wires when you're done, auto parts stores have rolls of the same stuff the manufacturers use. It looks like black electrical tape, but it's not sticky. Electrical tape will unravel into a gooey mess on a hot day. The wrap can be held at the ends with friction tape, or you can pull the end under the previous loop and pull it tight, like a knot.

I've never heard the term "microcomputer" inside another computer. What the person might have been referring to is the Transmission Computer is built into the Engine Computer.

We've covered all of the circuits related to the relay. That leaves the computer as the main suspect, but before I'd replace it, I'd use Chrysler's DRB3 scanner to turn that relay on. The scanner will cycle the relay on and off about once every two seconds. That will let you observe if the relay is clicking, and you can take voltage readings to find out which parts of the circuits are working.

Some aftermarket scanners have the same actuator test mode as the DRB3. Also, a lot of independent repair shops bought the Chrysler scanner because with an extra plug-in card, it will do emissions-related tests on all other brands of cars sold in the U.S. Starting with '96 models. You should be able to find a shop that can do these tests without having to go to the dealer.