P0688 jeep compass ошибка

Jeep Patriot P0688: Meaning, Causes, + Diagnosis

P0688 is a relatively rare OBD2 trouble code. It’s a generic code, meaning that it has the same definition for any vehicle made for the 1996 model year and up. This includes the Jeep Patriot.

The most common causes of P0688 are a bad PCM power relay or a wiring issue between the PCM and the power relay.

If your Patriot is still running with this code, we strongly recommend against driving with it. If the PCM power relay fails, your vehicle will not run properly.

P0688 Definition: PCM/ECM Power Relay Sense Circuit/Open

Here’s the definition of P0688 divided into its three distinct parts.

ECM/PCM Power Relay

ECM and PCM are interchangeable terms. They stand for engine control module and powertrain control module, respectfully. For this article, we will be referring to your Patriot’s main computer as the PCM exclusively.

The PCM Power relay circuit provides the proper voltage to the PCM when you turn the key to the on position. Here’s what’s typically involved in the circuit:

1. A ground wire
2. Power supply from the battery
3. Power from the ignition when the key is turned to the “on” position
4. Power relay sense circuit
5. Power to PCM

The sense circuit lets the PCM monitor the voltage at the PCM power relay circuit.

Sense Circuit Open

The sense circuit lets the PCM monitor the voltage at the PCM power relay. When your Jeep Patriot has P0688, it has detected an open circuit. If there is an open detected between the PCM and the PCM power relay, you’d have P0685.

An open circuit is a circuit that has not been completed. It means that no power is flowing through the PCM power relay control circuit to your Patriot’s PCM.

When this happens, P0688 will be stored in the PCM’s memory, and the check engine light will come on.

Jeep Patriot P0688 Symptoms

With this code, most of the time, the engine will not start or run. If it starts or runs, you’ll have to diagnose it differently.

• Hard/No start (mainly when it’s cold outside)
• Rough running engine
• Check engine light

P0688 Diagnosis + Causes

Below, you’ll find a diagnostic decision tree that should help determine what’s caused P0688 in your Jeep Patriot.

Remember, the circuit that senses the voltage at the power relay is open. So, either there’s no power going through it at all (which would suggest a bad relay or maybe a wiring problem). Or, the power relay is working just fine and the sense circuit has gone bad.

Either way, a good wiring diagram for your Jeep Patriot’s model year and engine type can go a long way in figuring out what’s causing P0688.

1. Will the Engine Start?

Yes– There’s either an intermittent wiring issue or a fault with the PCM. Check the NHTSA website to see if there are any technical service bulletins related to the PCM for your vehicle.

You should still check the wiring harness to make sure that there is no damage to it. Has your vehicle had any stalling issues, or run oddly? If it has had intermittent issues while running, it may be the wiring harness.

No– You’ll need to troubleshoot the PCM power relay circuit.

2. Inspect the PCM power relay circuit

Obtain a wiring diagram for the exact model year and engine combination for your Jeep Patriot. Most PCM relay terminals have 5 pins (covered above in the definition section, there are exceptions to this rule).

• If the engine seems to be operating just fine, take a good close look at the power relay sense circuit. It may be erroneously telling the PCM that there is an open. This is a very common cause of P0688 when the engine is still running fine.
• Is the relay getting a constant power supply from the battery? If it’s not, you will need to trace the harness back until you find where it’s damaged and repair it.
• Does the keyed power terminal have voltage when the key is in the on position? If there is no power coming from this power wire, check the fuse first. Make sure that it isn’t blown. Fuses rarely ever blow without a reason. If it is blown, check downstream of the fuse for open, short, or damaged wiring. Repair the harness as needed.
• Check the ground wire going to the harness. Verify that it is seated properly and not corroded.

3. Test the PCM Power Relay

If your Patriot won’t start and the relay is getting power from the battery pin and the keyed power pin (with a solid ground and a functioning PCM power relay sense wire), it’s time to suspect the PCM power relay itself.

Here’s a good video on how to test a relay. It’ll also give you a basic understanding of how they work if you’re having trouble with it.

4. Test the PCM

At this point, it’s time to have your Jeep Patriot’s PCM tested. We recommend taking it to a shop. Replacing or reflashing a PCM is best left to a mechanic. They’ll test the wiring harness first and make sure that you aren’t wasting money on a PCM you don’t need to clear P0688.

RECALLS! January 2022 Jason, “MAZDA6 shuts down while driving” fuel pump not monitored, may be no engine light etc. SEE…

I have a 2007 h3 hummer base model. Had transmission rebuilt (Pro).My problem is that when it gets around 35…

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2011 Jeep Compass No-Start

Car comes in with the complaint engine cranks doesn’t start. Confirm the complaint and check for codes, P0688 — ASD Relay Control Sense stored in memory. After doing a quick fuse check I found that fuses 23 and 26 at the Totally Integrated Power Module don’t have power. Visual inspection of the fusible links show they aren’t blown, other fuses check out OK. Where do these fuses get power? What’s the relationship between the no-start and the P0688?

1 Answer 1

First off, the P0688 code. What causes it to set?

• With ignition key on. Battery voltage greater than 10.0 Volts.
• The Powertrain Control Module (PCM) detects an open or short to ground in the (K51) ASD Relay control circuit. One Trip Fault. Three good trips to turn off the MIL.

OK so an open or short to ground on the relay control wire. That would make sense, the ASD relay supplies power to the fuel pump, injectors, coils etc. So if the relay control wire was open you’d never see power at these components.

As you see later this code doesn’t look only at the K51 circuit but seemingly the ASD circuit as a whole.

This one isn’t that intuitive, the way the diagram is laid out and how at first glance it makes you think that the TIPM provides power to the injector and coil fuses.

When you get to here it makes a bit more sense. You can see the K51 control wire and the A935 fused power wire.

So it’s time to locate the ASD relay.

In the left front fender well. You can see where this is going.

What was left of the spade connector that goes to the radiator fan relay.

Blast that with contact cleaner to clean it up a bit and smother it in dielectric grease.

Where the blue relay (radiator fan) is, the red/light blue wire is the one that rotted away. There was so much corrosion voltage dropped to 1v.

Like in the third wiring diagram you can see the ASD relay pulls power for the coil from the radiator fan relay.

Unfortunately no before fix pictures. It didn’t really occur to me to document this until I was done. This fix applies to a range of Chrysler products that use this platform.

Who knows why the relay box isn’t water proof. There aren’t even weather pack seals on the bottom as you can see in the last picture. There is a lower and upper cover (not shown) but neither is water tight.

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Jeep Compass P0688: Meaning, Causes, + Diagnosis

P0688 is a relatively rare OBD2 trouble code. It’s a generic code, meaning that it has the same definition for any vehicle made for the 1996 model year and up. This includes the Jeep Compass.

The most common causes of P0688 are a bad PCM power relay or a wiring issue between the PCM and the power relay.

If your Compass is still running with this code, we strongly recommend against driving with it. If the PCM power relay fails, your vehicle will not run properly.

P0688 Definition: PCM/ECM Power Relay Sense Circuit/Open

Here’s the definition of P0688 divided into its three distinct parts.

ECM/PCM Power Relay

ECM and PCM are interchangeable terms. They stand for engine control module and powertrain control module, respectfully. For this article, we will be referring to your Compass’s main computer as the PCM exclusively.

The PCM Power relay circuit provides the proper voltage to the PCM when you turn the key to the on position. Here’s what’s typically involved in the circuit:

1. A ground wire
2. Power supply from the battery
3. Power from the ignition when the key is turned to the “on” position
4. Power relay sense circuit
5. Power to PCM

The sense circuit lets the PCM monitor the voltage at the PCM power relay circuit.

Sense Circuit Open

The sense circuit lets the PCM monitor the voltage at the PCM power relay. When your Jeep Compass has P0688, it has detected an open circuit. If there is an open detected between the PCM and the PCM power relay, you’d have P0685.

An open circuit is a circuit that has not been completed. It means that no power is flowing through the PCM power relay control circuit to your Compass’s PCM.

When this happens, P0688 will be stored in the PCM’s memory, and the check engine light will come on.

Jeep Compass P0688 Symptoms

With this code, most of the time, the engine will not start or run. If it starts or runs, you’ll have to diagnose it differently.

• Hard/No start (mainly when it’s cold outside)
• Rough running engine
• Check engine light

P0688 Diagnosis + Causes

Below, you’ll find a diagnostic decision tree that should help determine what’s caused P0688 in your Jeep Compass.

Remember, the circuit that senses the voltage at the power relay is open. So, either there’s no power going through it at all (which would suggest a bad relay or maybe a wiring problem). Or, the power relay is working just fine and the sense circuit has gone bad.

Either way, a good wiring diagram for your Jeep Compass’s model year and engine type can go a long way in figuring out what’s causing P0688.

1. Will the Engine Start?

Yes– There’s either an intermittent wiring issue or a fault with the PCM. Check the NHTSA website to see if there are any technical service bulletins related to the PCM for your vehicle.

You should still check the wiring harness to make sure that there is no damage to it. Has your vehicle had any stalling issues, or run oddly? If it has had intermittent issues while running, it may be the wiring harness.

No– You’ll need to troubleshoot the PCM power relay circuit.

2. Inspect the PCM power relay circuit

Obtain a wiring diagram for the exact model year and engine combination for your Jeep Compass. Most PCM relay terminals have 5 pins (covered above in the definition section, there are exceptions to this rule).

• If the engine seems to be operating just fine, take a good close look at the power relay sense circuit. It may be erroneously telling the PCM that there is an open. This is a very common cause of P0688 when the engine is still running fine.
• Is the relay getting a constant power supply from the battery? If it’s not, you will need to trace the harness back until you find where it’s damaged and repair it.
• Does the keyed power terminal have voltage when the key is in the on position? If there is no power coming from this power wire, check the fuse first. Make sure that it isn’t blown. Fuses rarely ever blow without a reason. If it is blown, check downstream of the fuse for open, short, or damaged wiring. Repair the harness as needed.
• Check the ground wire going to the harness. Verify that it is seated properly and not corroded.

3. Test the PCM Power Relay

If your Compass won’t start and the relay is getting power from the battery pin and the keyed power pin (with a solid ground and a functioning PCM power relay sense wire), it’s time to suspect the PCM power relay itself.

Here’s a good video on how to test a relay. It’ll also give you a basic understanding of how they work if you’re having trouble with it.

4. Test the PCM

At this point, it’s time to have your Jeep Compass’s PCM tested. We recommend taking it to a shop. Replacing or reflashing a PCM is best left to a mechanic. They’ll test the wiring harness first and make sure that you aren’t wasting money on a PCM you don’t need to clear P0688.

RECALLS! January 2022 Jason, “MAZDA6 shuts down while driving” fuel pump not monitored, may be no engine light etc. SEE…

I have a 2007 h3 hummer base model. Had transmission rebuilt (Pro).My problem is that when it gets around 35…

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